Implement iOS app install deltas - #77756

Incremental iOS installs (app-deltas) are an Xcode feature exposed by ios-deploy in ios-control/ios-deploy#434 that saves a representation of the app to a place on disk, then only copies the deltas over when installing. Only implemented for BuildableIOSApp at build/ios/app-deltas, not PrebuiltIOSApp since I wasn't sure where the app deltas directory should live.

The app delta calculations are based on time stamp changes, not on file content hashes, so instead of deleting build/ios/iphoneos and copying the app bundle on every build, instead rsync the bundle so it only updates changed files, thus preserving the timestamps of unchanged files.

I ran some numbers (on my machine an an iPhone 6s) building and installing the new non-trivial gallery app after a flutter clean
The first number is the amount of time flutter run takes where I force an exit as soon as the app is launched. The second number is the same, run a second time with no clean.

So the improvements with thinning (#76834 and #77007), bitcode stripping (#77329), and codesigning (#77664) improved matters by ~3 seconds. App deltas gave us another ~14 seconds. It also cost us ~3 seconds on a first run, presumably to build the initial app-delta disk representation.

Note as long as flutter clean isn't run this will also be an improvement if any dart code changes and the App.framework needs to be recompiled, since the large Flutter.framework and plugin frameworks won't be copied over on subsequent installs.

BuildableIOSApp part of #67580.