Replace android sync framework result class with our own

[sunkup]

Purpose

More control over the sync result and less dependency on android.

Short description

1. Add our own SyncResult data class with the following differences:

• Not parcelable
• Replaced databaseError with localStorageError and contentProviderError; Updated it's usages.
• dropped methods, because unused:
  • madeSomeProgress()
  • clear()
  • describeContents()
  • writeToParcel()
  • toDebugString()
• dropped properties, because unused:
  • fullSyncRequested
  • moreRecordsToGet
  • partialSyncUnavailable
  • syncAlreadyInProgress
  • tooManyDeletions
  • tooManyRetries

2. Add our own SyncStats data class with the following differences:

• Not parcelable
• dropped properties, because unused or replaced:
  • numConflictDetectedExceptions (unused)
  • numParseExceptions (replaced by numDeadObjectExceptions and numServiceUnavailableExceptions)
• added properties, to avoid overloading existing properties:
  • numHttpExceptions
  • numUnclassifiedErrors
  • numDeadObjectExceptions
  • numServiceUnavailableExceptions

3. Tests ... to be added after first review

Note

• I have not added SyncResult to BaseSyncWorker even though it's the only place where it's used, bacause BaseSyncWorker is a damn long file already.

• I have not added tests yet because I am afraid there will be wishes for changes in the design.

Further Information
https://developer.android.com/reference/android/content/SyncResult

Checklist

• The PR has a proper title, description and label.
• I have self-reviewed the PR.
• I have added documentation to complex functions and functions that can be used by other modules.
• I have added reasonable tests or consciously decided to not add tests.

[ArnyminerZ]

Looks good. It's really odd to me to see data classes with vars and vals, but according to Kotlin it's valid sooo

[rfc2822]

Nice. Now we have it under our control, so we can further adapt it in the future, for instance drop / adapt the SyncStats etc.