[CI] Implement new cross-platform mock server

[testableapple]

🔗 Issue Links

Resolve https://linear.app/stream/issue/IOS-932

🎯 Goal

Share mock server across mobile platforms.

🛠 Implementation

• Get rid of Swifter
• Implement a custom mock server using Sinatra
• Move all the existing ruby/sinatra scripts to the mock server
• Unblock some tests that were blocked due to Swifter flakiness
• Comment out the iOS 16 e2e cron check due to unexpected hanging (also happens on develop)

📝 Notes

• This PR is a copy-paste from [CI][v5] Implement new cross-platform mock server #1085
• Mock server related PR.
• Android related PR.
• UIKit related PR.
• Code review and old Xcode checks also fail on v5 branch, keeping them as they are to avoid overcomplicating this PR.

🧪 Testing

On CI:

• Cron checks

Locally:

bundle exec fastlane start_mock_server
bundle exec fastlane test_e2e_mock device:"iPhone 17" # or run any test(s) on Xcode
bundle exec fastlane stop_mock_server

[github-actions]

	1 Warning
⚠️	Big PR

	1 Message
📖	There seems to be app changes but CHANGELOG wasn't modified. Please include an entry if the PR includes user-facing changes. You can find it at CHANGELOG.md.

Generated by 🚫 Danger

[github-actions]

Public Interface

🚀 No changes affecting the public interface.

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
StreamChatSwiftUI	9.78 MB	9.78 MB	0 KB	🟢

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud