x/auth should not depend on x/bank

[kocubinski]

x/bank will depend on x/auth, but x/auth should not depend on x/bank. This issue enumerates expressions of the dependency relationship x/auth -> x/bank and their solutions.

• ante/testutil_test.go - consider moving the test to /tests/integration or refactoring the suite to not directly depend on x/bank.
• migrations/v2/store_test.go - introduces a dependency on x/bank and x/staking, consider moving to /tests/integration. (handled in refactor(x/auth): rm dependency on x/staking #16545)
• migrations/v2/store.go - since we're marshaling/unmarshaling messages, these x/bank generated gogo types can be changed to the pulsar types in api.
• auth/expected_keepers.go - implement a parallel DenomMetadataV2 next to the existing bank/keeper.DenomMetadata (with comments explaining why) which accepts pulsar types instead of gogotypes. Use this in expected_keepers.go instead.
• legacy_amino_json_test.go - either use a message from x/auth instead of bank.MsgSend in tests or move this test to /tests/integration, this encoder is deprecated anyway.