Update jackson-databind-nullable to v0.2.9

[wing328]

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Summary by cubic

Updated all Java generator templates and samples to use jackson-databind-nullable v0.2.9, keeping dependencies current and consistent across build systems.

• Dependencies
  • Bumped org.openapitools:jackson-databind-nullable from 0.2.8 to 0.2.9 in Maven/Gradle/SBT templates where openApiNullable is used (apache-httpclient, feign, jersey2/3, okhttp-gson, rest-assured, restclient, resttemplate, retrofit2, vertx, webclient, helidon, Spring, JAX-RS, Camel) and corresponding samples.

^{Written for commit ffaa044. Summary will update on new commits.}

[wing328]

jaxrs-spec issues not related to this change. Tracked via #22902

[cubic-dev-ai]

No issues found across 241 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.