Unexpected compile time errors for finals with no initializer

[nshahan]

Possibly a duplicate of #43285.

Failing tests:

language/final/syntax_test/01
language/final/syntax_test/02

Errors:

org-dartlang-app:/out/ReleaseX64/generated_tests/language/final/syntax_test_01.dart:9:9: Error: The final variable 'f1' must be initialized.
Try adding an initializer ('= expression') to the declaration.
  final f1; //# 01: ok
        ^^

org-dartlang-app:/out/ReleaseX64/generated_tests/language/final/syntax_test_02.dart:11:13: Error: The final variable 'f3' must be initialized.
Try adding an initializer ('= expression') to the declaration.
  final int f3; //# 02: ok
            ^^

@johnniwinther

[leafpetersen]

This work (and tests) is tracked here: #43099