[analyzer] add null safety expectations to various tests

[asashour]

There are 6 places in tests with todos referring to #44666, which is now closed.

Would it make sense to just migrate the tests to NNBD (removing pre-nnbd expectations), or they can remain but only the expectation differ like in

sdk/pkg/analyzer/test/src/diagnostics/dead_code_test.dart

Line 114 in b15da0b

isNullSafetyEnabled ? [error(HintCode.DEAD_CODE, 66, 2)] : [],

The places are:

sdk/pkg/analyzer/test/generated/resolver_test_case.dart

Line 295 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

sdk/pkg/analyzer/test/generated/invalid_code_test.dart

Line 90 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

sdk/pkg/analyzer/test/src/diagnostics/inconsistent_language_version_override_test.dart

Line 21 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

sdk/pkg/analyzer/test/src/diagnostics/not_null_aware_null_spread_test.dart

Line 19 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

sdk/pkg/analyzer/test/src/task/strong/checker_test.dart

Line 18 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

sdk/pkg/analyzer/test/src/task/strong/inferred_type_test.dart

Line 22 in b15da0b

// TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in

[bwilkerson]

My opinion is that we do not want to remove the tests for pre-null-safety yet. The issue was about changing the default setting for new tests, not about changing existing tests. I think it was the wrong issue to have referenced in these cases.

[asashour]

https://dart-review.googlesource.com/c/sdk/+/280080 for InferredTypeTest.

Please note specially two test cases, were duplicated, one time for null safety and another for without null safety. With null safety, one test case passes, while the other passes because of timeout.

[asashour]

https://dart-review.googlesource.com/c/sdk/+/280115