[Wildcard Variables] support for `CONFLICTING_TYPE_VARIABLE_AND_MEMBER`

[pq]

For example, https://dart-ci.appspot.com/log/any/analyzer-asserts-linux/25914/language/wildcard_variables/declarations/class_generic_type_parameter_test:

--- Command "dart2analyzer" (took 41ms):
DART_CONFIGURATION=ReleaseX64 out/ReleaseX64/dart-sdk/bin/dart out/ReleaseX64/gen/dartanalyzer.dart.snapshot -Dtest_runner.configuration=analyzer-asserts-linux --enable-experiment=wildcard-variables --ignore-unrecognized-flags --packages=/b/s/w/ir/cache/builder/sdk/.dart_tool/package_config.json --format=json /b/s/w/ir/cache/builder/sdk/tests/language/wildcard_variables/declarations/class_generic_type_parameter_test.dart

unexpected analysis errors in class_generic_type_parameter_test.dart:
- Line 23, column 9: COMPILE_TIME_ERROR.CONFLICTING_TYPE_VARIABLE_AND_MEMBER
  '_' can't be used to name both a type variable and a member in this class.

- Line 23, column 12: COMPILE_TIME_ERROR.CONFLICTING_TYPE_VARIABLE_AND_MEMBER
  '_' can't be used to name both a type variable and a member in this class.

--- Re-run this test:
python3 tools/test.py -n analyzer-asserts-linux language/wildcard_variables/declarations/class_generic_type_parameter_test