Remove need for explicit `Config::async_support` knob (#12371)

* Refactor component model host function definitions

Push the `async`-ness down one layer.

* Remove need for explicit `Config::async

Remove need for explicit `Config::async_support` knob (#12371)

* Refactor component model host function definitions

Push the `async`-ness down one layer.

* Remove need for explicit `Config::async_support` knob

This commit is an attempt to step towards reconciling "old async" and
"new async" in Wasmtime. The old async style is the original async
support in Wasmtime with `call_async`, `func_wrap_async`, etc, where the
main property is that the store is "locked" during an async operation.
Put another way, a store can only execute at most one async operation at
a time. This is in contrast to "new async" support in Wasmtime with the
component-model-async (WASIp3) support, where stores can have more than
one async operation in flight at once.

This commit does not fully reconcile these differences, but it does
remove one hurdle along the way: `Config::async_support`. Since the
beginning of Wasmtime this configuration knob has existed to explicitly
demarcate a config/engine/store as "this thing requires `async` stuff
internally." This has started to make less and less sense over time
where the line between sync and async has become more murky with WASIp3
where the two worlds comingle. The goal of this commit is to deprecate
`Config::async_support` and make the function not actually do anything.

In isolation this can't simply be done, however, because there are many
load-bearing aspects of Wasmtime that rely on this `async_support` knob.
For example once epochs + yielding are enabled it's required that all
Wasm is executed on a fiber lest it hit an epoch and not know how to
yield. That means that this commit is not a simple removal of
`async_support` but instead a refactoring/rearchitecting of how async is
used internally within Wasmtime. The high-level ideas within Wasmtime
now are:

* A `Store` has a "requires async" boolean stored within it.
* All configuration options which end up requiring async, such as
yielding with epochs, turn this boolean on.
* Creation of host functions which use async
(e.g. `func_wrap_{async,concurrent}`) will also turn this option on.
* Synchronous API entrypoints into Wasmtime ensure that this boolean is
disabled.
* Asynchronous APIs are usable at any time.

This means that the concept of an async store vs a sync store is now
gone. All stores are equally capable of executing sync/async, and the
change now is that dynamically some stores will require that async is
used with certain configuration. Additionally all panicking conditions
around `async_support` have been converted to errors instead. All
relevant APIs already returned an error and things are murky enough now
that it's not necessarily trivial to get this right at the embedder
level. In the interest of avoiding panics all detected async mismatches
are now first-class `wasmtime::Error` values.

The end result of this commit is that `Config::async_support` is a
deprecated `#[doc(hidden)]` function that does nothing. While many
internal changes happened as well as having new tests for all this sort
of behavior this is not expected to have a great impact on external
consumers. In general a deletion of `async_support(true)` is in theory
all that's required. This is intended to make it easier to think about
async/sync/etc in the future with WASIp3 and eventually reconcile
`func_wrap_async` and `func_wrap_concurrent` for example. That's left
for future refactorings however.

prtest:full

* Review comments

* Fix CI failures

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Exceptions: fix panic in `is_vmgcref_type()` for `HeapType::Exn`. (#11535)

* Exceptions: fix panic in `is_vmgcref_type()` for `HeapType::Exn`.

Fixes #11529 (for real this time).

* Add test.

Support exceptions with Pulley (#11495)

* Support exceptions with Pulley

This implements Chris's suggestion to avoid special-casing the `raise`
libcall and instead let it fully execute for Pulley.

Support exceptions with Pulley (#11495)

* Support exceptions with Pulley

This implements Chris's suggestion to avoid special-casing the `raise`
libcall and instead let it fully execute for Pulley. The switch of
whether to do a native longjmp or a Pulley longjmp is done based on the
interpreter state of Wasmtime's configured executor.

Closes #11486

prtest:full

* Resolve a TODO

* Ignore tests on miri that compile wasm

* Fix configured builds

* Undo typo

* Fix another typo

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WebAssembly exception-handling support. (#11326)

* WebAssembly exception-handling support.

This PR introduces support for the [Wasm exception-handling proposal],
which introduces a conventional try

WebAssembly exception-handling support. (#11326)

* WebAssembly exception-handling support.

This PR introduces support for the [Wasm exception-handling proposal],
which introduces a conventional try/catch mechanism to WebAssembly. The
PR supports modules that use `try_table` to register handlers for a
lexical scope; and provides `throw` and `throw_ref` that allocate (in
the first case) and throw exception objects.

This PR builds on top of the work in #10510 for Cranelift-level
exception support, #10919 for an unwinder, and #11230 for exception
objects built on top of GC, in addition a bunch of smaller fix and
enabling PRs around those.

[Wasm exception-handling proposal]: https://github.com/WebAssembly/exception-handling/

prtest:full

* Permit UnwindToWasm to have unused fields in Pulley builds (for now).

* Resolve miri-caught reborrowing issue.

* Ignore exceptions tests in miri for now (Pulley not supported).

* Use wasmtime_test on exceptions tests.

* Get tests passing on pulley platforms

* Add a check to `supports_host` for the generated test and assert
failure also when that is false.
* Remove `pulley_unsupported` test as it falls out of `#[wasmtime_test]`
* Remove `exceptions_store` helper as it falls out of `#[wasmtime_test]`
* Remove miri annotations as they fall out of `#[wasmtime_test]`

* Remove dead import

* Skip some unsupported tests entirely in `#[wasmtime_test]`

If the selected compiler doesn't support the host at all then there's no
need to run it. Actually running it could misinterpret `CraneliftNative`
as "run with pulley" otherwise, so avoid such false negatives.

* Cranelift: dynamic contexts: account for outgoing-args area.

---------

Co-authored-by: Alex Crichton <[email protected]>

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