Move tests for switch enum cases for >= 2.19 from `AddMissingEnumCase…

…ClausesTest` to `AddMissingSwitchCasesTest_SwitchStatement`

The tests in this class were duplicated when pattern support was added, one set
of tests for <= 2.19 and one for > 2.19. The> 2.19 tests were marked as Failing
because this functionality didn't work.

This functionality has now been implemented, but because the error code and fix
are different, these tests continued to fail. This change moves the tests to
the equivalent pattern-enabled fixes tests and removes `@FailingTest` for
those that can now pass.

There are still a few marked `@FailingTest` because of differences in the new
implementation.

See #52180 (comment)

Change-Id: Ie1dfa5bc5c608d38a191507f5f0403d20ba2ef31
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/371684
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Sam Rawlins <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>