feat(conflict): Add MySQL backed target dictionary store

[manjari25]

Why?

Signatures hold 64-bit hashes, not labels. To explain or debug a conflict, someone needs to map an ID back to the target label it stands for. This PR implements the DictionaryStore contract from the first PR in the stack on MySQL, as part of the package owned by the tango conflict extension.

What?

Everything is added under submitqueue/extension/conflict/tango/mysql:

• Adds the target_dictionary table:
  • Primary key (queue, id), with no secondary index.
  • The label is a plain TEXT value column.
  • A row is written once and never updated.
• Adds a queue-bound MySQL DictionaryStore:
  • Create returns storage.ErrAlreadyExists if the ID is already recorded, even with a different label, so the first label on a hash collision stays.
  • A label whose queue differs from the bound queue is rejected.
  • Get reports an unrecorded ID as found=false, not as an error.
• Extends the integration suite from the previous PR with a dictionary test. It covers an ID with the high bit set (the unsigned column), a long label, a second label keeping the first, and queue isolation. Both stores now share one suite and one MySQL container, so the suite type is renamed.
• The store is not added to the orchestrator Storage aggregate. Nothing constructs it yet.

Test Plan

./tool/bazel test //submitqueue/extension/conflict/tango/mysql:go_default_test
./tool/bazel test //test/integration/submitqueue/extension/conflict/tango/mysql/... --test_output=streamed
make check-gazelle
make check-mocks
make lint
CI

Issue