[Java][WebClient] Add @Deprecated to main and WithResponseSpec methods of deprecated operations

[ondrej-simon]

Fixes #25127.

For a deprecated operation, the Java webclient library generates three public methods, but only operationWithHttpInfo(...) was annotated with @Deprecated (added in #23039). This PR adds the same @Deprecated annotation and @deprecated Javadoc tag to the other two public methods, operation(...) and operationWithResponseSpec(...), so that all entry points of a deprecated endpoint trigger deprecation warnings (e.g. with javac -Xlint:deprecation -Werror). This also covers the method originally reported in #22675.

Changes:

• Java/libraries/webclient/api.mustache: add {{#isDeprecated}} blocks to {{operationId}} and {{operationId}}WithResponseSpec.
• New test JavaClientCodegenTest#testWebClientDeprecatedOperation: asserts all three methods of the deprecated findPetsByTags are annotated, and none of the non-deprecated findPetsByStatus are. The test fails without the template change.
• Regenerated bin/configs/java-webclient*.yaml samples (no other configs use the webclient library). Only the four petstore PetApi.java samples containing the deprecated findPetsByTags operation change.

PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

cc Java technical committee: @bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608 @martin-mfg @KannaKim

---

Summary by cubic

Fixes #25127. Applies the @Deprecated annotation and @deprecated Javadoc tag to the operation(...) and operationWithResponseSpec(...) methods of deprecated operations in the Java webclient library, matching the existing annotation on operationWithHttpInfo(...) so all entry points trigger deprecation warnings.

• Adds a regression test asserting all three methods of a deprecated operation are annotated and carry the @deprecated Javadoc tag, while deprecated methods of non-deprecated operations remain untouched.
• Regenerates java-webclient* sample PetApi.java files affected by the template change.

^{Written for commit 6f3379f. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 6 files

<sub>Reply to a comment to ask cubic a question or push back. It learns from your replies.

Re-trigger cubic</sub>