Various browser build updates & fixes

[dnzxy]

Contents

• Bump fastlane to 2.220.0
• Bump action container OS from macos-13 to macOS-14
• Bump Xcode selection to latest stable 15.3 (15.4 still in beta; cf. GitHub action runner-images macos-14 Readme)
• Replace GH-provided GITHUB_TOKEN with user-provided GH_PAT around alive functionalities

Why this PR?
Please see Loop PRs LoopKit/LoopWorkspace#125 and LoopKit/LoopWorkspace#126
Furthermore, to demonstrate the issue: without this update actions are failing.
Failed actions (pre-update; based on latest staging-5.2) see here:

• Validate Secrets: implicitely run as sub-steps.
• Add Identifiers: https://github.com/dnzxy/xdripswift/actions/runs/8913545608
• Create Certificates: https://github.com/dnzxy/xdripswift/actions/runs/8913618682
• Build Build xDrip4iOS: https://github.com/dnzxy/xdripswift/actions/runs/8913658034
• Also, failed scheduled build here: https://github.com/dnzxy/xdripswift/actions/runs/8907072658 (based on master)

Tests
Tested by running all actions (in conjunction with previously having built another app that writes to the same Match-Secrets repository). Successfully run actions:

• Validate Secrets: implicitely run as sub-steps.
• Add Identifiers: https://github.com/dnzxy/xdripswift/actions/runs/8913583414
• Create Certificates: https://github.com/dnzxy/xdripswift/actions/runs/8913637317
• Build Build xDrip4iOS: https://github.com/dnzxy/xdripswift/actions/runs/8913678599

Edit to add: This PR addresses and solves #521.