251303f28f
The old `native "<name>"` syntax was lowered to `@ExternalName()`
annotations. Those have been deprecated in favor of
`@pragma('vm:external-name')`. Users have now been migrated and we can
therefore remove the VM support for `@ExternalName`.
Issue https://github.com/dart-lang/sdk/issues/28791
TEST=ci
Change-Id: I69febe49f59627659c540dd50ad0fbf704b6c3a7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/266387
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>