refactor: remove MemberShape location_name alias and regenerate projections

[jterapin]

Context

Stacked on #355.

The earlier schema extension PRs moved runtime serde toward model_name while keeping location_name as a temporary compatibility alias on MemberShape. This follow-up removes that alias inside smithy-ruby and updates the checked-in generated projections to emit model_name.

What changed

• removed the location_name fallback and alias from Smithy::Schema::Shapes::MemberShape
• updated smithy-client call sites that still referenced location_name
• updated the serde interface spec to assert model_name
• regenerated the checked-in projection schemas so generated output now emits model_name

Scope

This PR is intentionally limited to smithy-ruby and its checked-in projections.

Out of scope for this PR:

• downstream aws-sdk-core runtime call sites that still reference location_name
• regenerating downstream staged service schemas that still emit location_name

Testing

• bundle exec smithy build --debug
• bundle exec rspec gems/smithy-schema/spec/smithy-schema/shapes_spec.rb
• bundle exec rspec gems/smithy/spec/interfaces/schema/serde_traits_spec.rb
• bundle exec rspec gems/smithy-client/spec/smithy-client/plugins/host_prefix_spec.rb
• bundle exec rspec gems/smithy-client/spec/smithy-client/plugins/stub_responses_spec.rb
• bundle exec rake smithy-cbor:spec smithy-client:spec smithy-json:spec smithy-schema:spec smithy-xml:spec smithy:spec

--
Written with AI assistance and reviewed by jterapin.