[co19] Roll co19 to 6604c07f70757e9d081f64a08ab36f5b9aeaf937
[co19] Roll co19 to 6604c07f70757e9d081f64a08ab36f5b9aeaf937

2022-03-31 519320+chloestefantsova@users.noreply.github.com Adjust locations of errors reported by CFE in Enhanced Enums tests (dart-lang/co19#1334)
2022-03-29 519320+chloestefantsova@users.noreply.github.com Remove extra expected CFE errors that are no longer reported (dart-lang/co19#1331)
2022-03-29 519320+chloestefantsova@users.noreply.github.com Add expected CFE errors on concrete 'index' members (dart-lang/co19#1330)
2022-03-29 519320+chloestefantsova@users.noreply.github.com Remove unused and uninitialized non-nullable field from a test (dart-lang/co19#1329)

Change-Id: Ic2a234038c69871af4e3179de2fb10c5c6a4015a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/240050
Auto-Submit: Alexander Thomas <29642742b6693024c89de8232f2e2542cf7eedf7@google.com>
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>
Commit-Queue: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@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