[release] Add 2.17.4 release notes
[release] Add 2.17.4 release notes

This is a patch release that fixes:

- Improve analysis of enums and switch (issue [#49188]).
- Fix compiler crash when initializing Finalizable objects (issue [#49075]).

[#49188]: https://github.com/dart-lang/sdk/issues/49188
[#49075]: https://github.com/dart-lang/sdk/issues/49075

Change-Id: If2059474ce2acbadf7f3c6e407f0087d262e2842
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/249161
Reviewed-by: Michael Thomsen <5977a55c75bb4612004451a56b0b4c22d9d3311d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk