feat: [Rust][client] Add option to use rustls for reqwest instead of openssl

[aran]

Generated Rust crates will allow configuring reqwest to use rustls via passthrough features.

fix: #19853

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 Git BASH)
  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 is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request. @frol @farcaller @richardwhiuk @paladinzh @jacob-pro

[wing328]

@aran thanks for the PR

allow configuring reqwest to use rustls via passthrough features.

I wonder if you can reply with some code snippets as examples showing how to do that.

[aran]

Say I have a crate generated by openapi called mycrate. The user of mycrate would do:

mycrate = { version = "^1.0.0", default-features = false, features = ["rustls"] }

[wing328]

thanks. if no one has further question/feedback, i'll merge this PR later this week