Rely on `core::error::Error` (#9702)

* Rely on `core::error::Error`

With Wasmtime's new MSRV at 1.81 this means that `core::error::Error` is
available which means that in `no_std` mode the `Error`

Rely on `core::error::Error` (#9702)

* Rely on `core::error::Error`

With Wasmtime's new MSRV at 1.81 this means that `core::error::Error` is
available which means that in `no_std` mode the `Error` trait can be
used. This has been integrated into `anyhow::Error` already upstream and
means that we can remove our own local hacks such as the `Err2Anyhow` trait.

This commit removes the `Err2Anyhow` trait and all usage, going back to
idiomatic Rust error propagation and conversion even in the `no_std`
world. This should make code more portable by default and remove some
weird idioms we had for supporting this.

prtest:full

* Add some trusted vets

* Audit object crate update

* Disable backtraces on CI

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Move memory pool over to aligned byte counts (#9668)

* Move memory pool over to aligned byte counts

Part of work to centralize memory management within Mmap instances -- some of
that work becomes e

Move memory pool over to aligned byte counts (#9668)

* Move memory pool over to aligned byte counts

Part of work to centralize memory management within Mmap instances -- some of
that work becomes easier if the byte counts are known to be aligned.

There were a few overflow cases that I added checks for.

* Address review comments

* Fix unused code warnings

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Add HostAlignedByteCount to enforce alignment at compile time (#9620)

* Add HostAlignedByteCount to enforce alignment at compile time

As part of the work to allow mmaps to be backed by other implem

Add HostAlignedByteCount to enforce alignment at compile time (#9620)

* Add HostAlignedByteCount to enforce alignment at compile time

As part of the work to allow mmaps to be backed by other implementations, I
realized that we didn't have any way to track whether a particular usize is
host-page-aligned at compile time.

Add a `HostAlignedByteCount` which tracks that a particular usize is aligned to
the host page size. This also does not expose safe unchecked arithmetic
operations, to ensure that overflows always error out.

With `HostAlignedByteCount`, a lot of runtime checks can go away thanks to the
type-level assertion.

In the interest of keeping the diff relatively small, I haven't converted
everything over yet. More can be converted over as time permits.

* Make zero-sized mprotects a no-op, add tests

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