Test operation security alternatives

[kriptoburak]

Summary

• Add a parser regression for operation security with an anonymous alternative and an API key requirement.
• Assert both operation-level security requirement entries are preserved.

Validation

• Static whitespace check passed before commit.
• Not run: this environment does not have a Java runtime or Maven.

[kriptoburak]

Rebased onto the current master branch at 4467854473a2a3a8b70413aeecaa279100491d5f. git range-diff confirms the regression patch is unchanged.

Local validation with JDK 21:

• OpenAPIDeserializerTest: 89 tests passed
• Reactor verify passed for swagger-parser-v3 and dependencies
• git diff --check passed

This remains a test-only change.