feat: gh pr related features

[armcknight]

Adds 3 things:

• the ability to open PRs for all branches of a chain using gh pr create --web --base <$git-chain-prev>
• list PR urls next to branches in git chain status
• list PR urls next to branches in git chain list

For those last two, I put the functionality behind a --pr flag because it's considerably slower.

example:

󰂃 9% ❯ git chain list --pr
feedback-widget-improvements
      armcknight/feedback/fix/5113-swiftui-widget-injection ⦁ 1 ahead ⦁ 12 behind
      armcknight/feedback/feat/4767-bring-your-own-button ⦁ 8 ahead ⦁ 16 behind
      main (root branch)

macos-launch-profile-hotfix-8.49.2
      armcknight/ci/macos-sample-app-profiling ⦁ 14 ahead ⦁ 1 behind (https://github.com/getsentry/sentry-cocoa/pull/5146)
      armcknight/profiling/fix/mac-app-nonsandboxed-launch-profiling ⦁ 18 ahead ⦁ 1 behind
      armcknight/profiling/test/mac-app-launch-profiling-config-file ⦁ 13 ahead
      hotfix/8.49.2 (root branch)

sample-app-shared-sdk-lib
      armcknight/test/schema-configs ⦁ 7 ahead
      armcknight/test/shared-sdk-wrapper-other-platforms ⦁ 11 ahead ⦁ 2 behind
      armcknight/test/share-sdk-wrapper ⦁ 38 ahead ⦁ 229 behind
      armcknight/meta/correct-version-setting (root branch)

sample-app-xcodegen
      armcknight/ci/ios-objectivec-xcodegen ⦁ 4 ahead
      armcknight/ci/macos-swift-xcodegen ⦁ 3 ahead
      armcknight/ci/macos-swiftui-xcodegen ⦁ 4 ahead
      armcknight/ci/visionos-swift-xcodegen ⦁ 4 ahead
      armcknight/ci/ios15-swiftui-xcodegen ⦁ 4 ahead
    ➜ armcknight/ci/ios-swftui-xcodegen ⦁ 5 ahead
      armcknight/meta/correct-version-setting ⦁ 28 ahead (https://github.com/getsentry/sentry-cocoa/pull/5139)
      armcknight/ci/ios-swift-cleanup ⦁ 27 ahead (https://github.com/getsentry/sentry-cocoa/pull/5118)
      armcknight/ci/ios13-swift-xcodegen ⦁ 32 ahead (https://github.com/getsentry/sentry-cocoa/pull/5117)
      armcknight/ci/ios-swift6-xcodegen ⦁ 34 ahead (https://github.com/getsentry/sentry-cocoa/pull/5116)
      armcknight/ci/ios-swift-xcodegen ⦁ 55 ahead ⦁ 2 behind (https://github.com/getsentry/sentry-cocoa/pull/5115)
      armcknight/ci/camera-sample-with-xcodegen ⦁ 32 ahead (https://github.com/getsentry/sentry-cocoa/pull/5106)
      main (root branch)

ui-profiling-fixes
      armcknight/test/reproduce-root-span-tracking-issue ⦁ 6 ahead ⦁ 51 behind (https://github.com/getsentry/sentry-cocoa/pull/5071)
      main (root branch)

[armcknight]

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