[JAVA] use JsonTypeInfo.Id.DEDUCTION for oneOf interface

[jpfinne]

same as #20919 for java generators.

Fix #20891 (for java)

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Summary by cubic

Adds optional Jackson deduction for generated Java oneOf interfaces without discriminator mappings. This enables structure-based deserialization with @JsonTypeInfo(use = DEDUCTION) and @JsonSubTypes.

• New Features

  • New flag useDeductionForOneOfInterfaces (works with useOneOfInterfaces) to emit @JsonTypeInfo(use = JsonTypeInfo.Id.DEDUCTION) and @JsonSubTypes on oneOf interfaces without discriminators.
  • Exposed in JavaClientCodegen CLI; documented in docs/generators/java.md and docs/generators/java-microprofile.md. Test added in JavaClientCodegenTest.
  • Added Java/deductionAnnotation.mustache and integrated it into oneof_interface.mustache.

• Refactors

  • Centralized the option in AbstractJavaCodegen; removed the duplicated setting from SpringCodegen.

^{Written for commit 2311be0. Summary will update on new commits. Review in cubic}

[cubic-dev-ai]

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