Improved build performance

• Improve build performance when there are lots of built_value classes.

Fix for new `operator==` warning

• Fix for new warning about operator== param type.

StandardJsonPlugin improvement, EnumClass fix

• In StandardJsonPlugin, add support for specifying types that should be left as List.
• Allow non alphanumeric characters in EnumClass names.

Allow serializing record fields

• Allow classes with record fields to be serialized if they use a typedef for
  the record type and install a custom Serializer for it.

Add `Int32` serializer

• Add Int32 serializer.

Bump version of `analyzer`

• Bump version of analyzer.

Remove JSON from error message, fix generation

• Remove JSON from DeserializationError message to prevent data accidentally
  leaking into logs. The JSON is still available on the DeserializationError
  object.
• Fix generation for fields that are Function types that are declared
  separately, for example in a mixin defined in another source file, and use
  named or positional parameters.

Fix mixin generation

• Fix support for generating enum mixins for Dart 3. Instead of triggering mixin generation with abstract class TestEnumMixin = Object with _$TestEnumMixin it must now be triggered with typedef TestEnumMixin = _$TestEnumMixin.

Records support

• Add support for value types with record fields. Serialization with records is not yet supported.
• Fix generator failure due to top level record field.
• Migrate benchmark and examples to null safety.
• Remove pre-null-safe test cases.
• Remove analyzer plugin.
• Remove reference to @nullable annotation from failure-to-instantiate message.

Dart 3 support, Uint8ListSerializer

• Add Uint8ListSerializer.
• Generate Dart-3-compatible code if needed.
• Stop using deprecated analyzer API.
• Fix codegen for optional fields with $ in the name.