Remove local web server & Carthage

[eneko]

• I've read, understood, and done my best to follow the CONTRIBUTING guidelines.

This pull request includes (pick all that apply):

• Bugfixes
• New features
• Breaking changes
• Documentation updates
• Unit tests
• Other

Summary

Conduit CI has been broken for a long time (since March 2020):

• Last successful cron build was 10 months ago
• Last successful PR build was also 10 months ago

This is mainly because the local web-server used for unit and integration tests was outdated. As new versions of Ruby and Python have been released, and our systems and CI servers upgraded, the local server stopped running. Quite some good tech-debt we had queued.

Implementation

• Remove local web servers
  • httpbin has been replaced with calls to https://httpbin.org (as we originally had). Video assets have been reduced in size for faster round-trips during testing.
  • oauth-test-server has been removed and not replaced (a handful of tests have been disabled for now)
• Project and workspace files have been removed to simplify the codebase and maintenance efforts.
• Carthage support has also been removed, might be added later as XCFramework if there is public demand.
• Travis CI has been removed
• GitHub Actions have been set up for CI

Test Plan

• Run all tests with swift test or from Xcode

[tiltem]

Is there anyway to not disable those tests?

[eneko]

@tiltem this subset of tests have been broken for a long time (since CI stopped running). I've been looking for a replacement for oauth-test-server, but unfortunately haven't found a good solution yet. My intention is to have those tests running later on.

I've added AB#937603 to track this work.