Debugging: add the debug-main world. (#12756)

* Debugging: add the debug-main world.

This PR "draws the rest of the owl" for the debug-main
world (bytecodealliance/rfcs#45). This includes a WIT wor

Debugging: add the debug-main world. (#12756)

* Debugging: add the debug-main world.

This PR "draws the rest of the owl" for the debug-main
world (bytecodealliance/rfcs#45). This includes a WIT world that hosts
debug components that have access to "host debug powers" via a
debugging API, and the ability to load such a debug-component and give
it control of the main program as a debuggee when using `wasmtime
run`.

The WIT is namespaced to `bytecodealliance:wasmtime` and is slightly
aspirational in places: for example, the host does not yet implement
injection of early return values or exception-throws. I intend to fill
out a series of TODO issues once this all lands to track followup
("post-MVP") work.

This PR does not include any debug components. I separately have a
gdbstub component, with which I tested and co-developed this host-side
implementation. My plan is to land it in a followup PR as a component
that will be embedded in/shipped with the Wasmtime CLI and available
under an easy-to-use CLI option. Once we have that gdbstub component,
we can also implement end-to-end integration tests that boot up LLDB
and run through an expected interaction. (Separately, those
integration tests will require a release of wasi-sdk to ship an LLDB
binary that we can use.) As such, there are no real tests in this PR:
interesting behaviors only really occur with a full end-to-end flow.

The integration with the CLI is a little awkward (we internally build
another `wasmtime run` command that invokes the debug component, and
tie it together with the debuggee via a special `invoke_debugger` API;
this seemed less bad than reworking all of the WASI setup to be more
reusable). Happy to take more ideas here.

* Review feedback.

* Review feedback.

* Review feedback: update vendor-wit.sh.

* Review feedback: -Ddebugger-arg= -> -Darg=.

* Review feedback.

* Review feedback.

* Review feedback: factor host.rs into several submodules.

* Review feedback: rename Debugger to Debuggee on host side.

* Review feedback: split inherit_stdin_stdout, and add corresponding options for the debug component.

* Review feedback.

* Review feedback.

* Add simple debug-component tests.

* Add wasm32-wasip2 target in a few places in CI

* Cargo vets for wstd dependency.

* Add wasm32-wasip2 in more places

* fix debug-component test dependence on componentization byte offsets

* Review feedback.

* Fix cancel-safety of EventFuture.

* Fix: Interrupted events should only occur after interrupt(), not on every epoch yield.

* Review feedback.

* Review feedback: strip down WASI imports in debugger world.

* fold debugger test component back into wasip1 + adapter test artifact compilation flow

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