Add reqwest-trait crate to workspace and rename it

[dani-garcia]

The rust-request template is missing a check for the ^isArray case so when the parameter is an array, it generates both the #isArray variant and the ^isArray variant. This causes a compilation failure. This check is present in the request template, so this seems like an oversight: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator/src/main/resources/rust/reqwest/api.mustache#L211

The reason this was not caught by the tests is that the request-trait example crate was not added to the workspace, so it wasn't being built. As it was a small change, I've added it to the workspace in this PR and renamed the example crate to avoid a name collision, please let me know if you'd prefer a separate PR for that.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• 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.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR solves a reported issue, reference it using GitHub's linking syntax (e.g., having "fixes #123" present in the PR description)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request. @frol (2017/07) @farcaller (2017/08) @richardwhiuk (2019/07) @paladinzh (2020/05) @jacob-pro (2022/10) @dsteeley (2025/07)

[dsteeley]

Not directly impacting the changes in this PR. The tests for rust-server are failing due to an unrelated reason. I'm attempting a resolution in #21664 but likely won't get that sorted in the next week.

[dsteeley]

I'm not overly familiar with the rust generator but this change looks sensible to me.

[wing328]

rust server build failure not related to this pr

[wing328]

thanks for the PR

let's give it a try