Add await using Declarations and AsyncDisposableStack

[rbuckton]

This PR contains the Stage 2 specification text for Async Explicit Resource Management. If Async Explicit Resource Management advances to Stage 3, it's possible this may be merged with tc39#3000 to streamline advancement due to the layering of these proposals.

NOTE: esmeta checks for this PR won't succeed until we've updated the build process to use a version of esmeta containing es-meta/esmeta#134.

[michaelficarra]

NOTE: esmeta checks for this PR won't succeed until we've updated the build process to use a version of esmeta containing es-meta/esmeta#134.

If you let me know when they tag a release, I'll bump esmeta. For now, that commit hasn't even landed on their main branch yet, so I'm not inclined to depend on it.

[rbuckton]

@michaelficarra apparently es-meta/esmeta#134 was included in 0.3.3, though it doesn't show up in the release notes.

[michaelficarra]

@rbuckton It appears we are already using 0.3.3 in ecma262 CI: https://github.com/tc39/ecma262/blob/main/.github/workflows/esmeta-typecheck.yml#L27

Is there anything else I need to do here?

[rbuckton]

Is there anything else I need to do here?

It doesn't look like it, no.

[rbuckton]

This should now be up to date with the current consensus spec text, so I will merge this into the main PR.