#23904 Fix #23903 by using method parameter names that are guaranteed not to…

… conflict with variables in the same method.

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Summary by cubic

Prevents name collisions in generated Java RestClient methods by prefixing all method parameters with "__", fixing cases where params shadow local variables. Fixes #23903.

• Bug Fixes
  • Updated modules/openapi-generator/src/main/resources/Java/libraries/restclient/api.mustache to emit __paramName for all method parameters (including Javadoc).
  • Applied the change across query, path, header, form, multipart, and body handling in request-creation methods.
  • Regenerated Java RestClient samples and updated tests (e.g., expect if (__filter != null)), ensuring no param/variable conflicts.