Switch to UniFFI library mode [ci full]

[bendk]

I'm reviving #5592 and giving it another shot. If successful, this can be the basis for @gruberb's proc-macro work.

Pull Request checklist

• Breaking changes: This PR follows our breaking change policy
  • [x] This PR follows the breaking change policy:
    • This PR has no breaking API changes, or
    • There are corresponding PRs for our consumer applications that resolve the breaking changes and have been approved
• [x] Quality: This PR builds and tests run cleanly
  • Note:
    • For changes that need extra cross-platform testing, consider adding [ci full] to the PR title.
    • If this pull request includes a breaking change, consider cutting a new release after merging.
• [x] Tests: This PR includes thorough tests or an explanation of why it does not
• [x] Changelog: This PR includes a changelog entry in CHANGELOG.md or an explanation of why it does not need one
  • Any breaking changes to Swift or Kotlin binding APIs are noted explicitly
• [x] Dependencies: This PR follows our dependency management guidelines
  • Any new dependencies are accompanied by a summary of the due diligence applied in selecting them.

Branch builds: add [firefox-android: branch-name] to the PR title.

[bendk]

In that PR, Tarik said "Looks like this ended up being a breaking change for firefox-ios because of a swift name conflict". I completely forget what that means, but can someone test this code with a local ios build and see if it works?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 47.71%. Comparing base (8be45cd) to head (c00a8ea).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6341      +/-   ##
==========================================
- Coverage   49.30%   47.71%   -1.59%     
==========================================
  Files         146      162      +16     
  Lines       13708    14164     +456     
==========================================
  Hits         6759     6759              
- Misses       6949     7405     +456     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[bendk]

I tested a local Fenix build and it worked for me. @gruberb was able to get iOS to successfully compile. This seems like good enough evidence to me, but please tell me if we should test more.

@jeddai do you think we need to do any extra testing for cirrus?