Throw fewer deprecation warnings for the RawExtrinsicMetadata id attr
This avoids throwing the deprecation warning when id and target are present and have the same value, which makes a from_dict / to_dict round-trip throw no deprecation warnings.
This allows running pytest with -W error:RawExtrinsicMetadata:DeprecationWarning on other modules to migrate them away from the legacy attributes.
Test Plan
tox
Migrated from D4366 (view on Phabricator)