Cherry-pick #3784 into an 8.0.9+1 release

[srawlins]

The flutter roller is blocked and needs the fix in #3784 (14d33d3) released. Rather than cut a release with unrelated changes (with potential bugs), I'm cutting a cherry-pick release. This avoids ~10 commits between 8.0.9 and 14d33d3, and ~14 commits that have landed since the fix.

This PR actually contains three other cherry-pick commits that are necessary for CI (ddb8fb4, 3decf1e, ed97585) (CI was in a bad state right after 8.0.9 was released). They are all cherry-picked in the same order in which they appear on the main branch.

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[srawlins]

CC @dart-lang/analyzer-team

[bwilkerson]

I don't really understand what's blocking the roll or why this fixes it, but I don't see anything that raises red flags, so I'm approving it. (I didn't look at the .js files. I'm hoping those are generated and don't need a review.)

[srawlins]

Ah yeah, there isn't a ticket, as far as I know, for the roll being blocked. 🤷 But the issue appears to be that:

1. Someone landed code in the SDK. That code can be documented with dartdoc in the SDK because dartdoc in the SDK is up-to-date.
2. That code is rolling to flutter. Flutter does not use an up-to-date dartdoc; it uses a pub activated release from pub.
3. So now this code is tickling the dartdoc crashes when referring to the type parameter of a generic extension type with a typedef representation type #3783 bug, fixed by Fix referencing an aliased type parameter. #3784, cherry-picked here.