Port to Android 15

[grote]

• Build Android and Java libraries from AOSP source code that include the hidden APIs required for Seedvault and add them to the (gradle) buildsystem
• Identify all upgraded libraries and find matching versions for the non-AOSP buildsystem, bumping their versions as needed.
• Upgrade other libraries and include jar binaries as needed.
• Go through all backup related AOSP commits since last Android release and learn about changes, adapting Seedvault code as needed, especially for breaking changes preventing compilation.
• Include all work in a new pull request creating a new android15 branch of Seedvault.

Related to #564

[grote]

Folders in frameworks/base to monitor for changes since last release:

• core/java/android/app/backup
• packages/LocalTransport
• services/backup

[grote]

• Lots of new BackupMonitor events that can be helpful for debugging and reversing backup flows: https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/501eeee21a5fb200b88b42eb8ed53be67bd16e56
• https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/f361f21034557f267ce52d52ece48104606c3f22
  • eligibility conditions are now also checked before restore, in case the backup happened on a device / from the version of the app where these rules were not enforced
  • new internal backup_flags_lib
  • Flag for RestoreSet#backupTransportFlags to indicate if restore should be skipped for apps that have already been launched (not clear what this means and how it would affect restore after SUW)
• new flag for enabling the write buffer to pipes to be of maximum size. We should probably enable this. https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/a10db39e59274a2abaa7e5b47d248069c2c853cf
• restore bug fix that needs an active flag to work? https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/d13c86c09694fd9e5ee1ccfad031a741f6af5cc9
• better logging for auto-restore at install behind a flag: https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/f11e886dc73bb52ad2b4f9c8225c322cfa383de5
• there seem to be issues with restoring a 15 backup on a 14 device: https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/e8deecf6a9cad1f0e17add7b7f0e7be0d2e65d28
• some new team members working on backup: https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/74e809c0cd0c7e935ca0c631ba93f3776025f730
• some background for the mysterious ancestral record in this commit message: https://gitlab.com/CalyxOS/platform_frameworks_base/-/commit/8d8a538cab07b49793fc7c91a6e7374fb676d1c9

[theimpulson]

Related: #742