[DataStore] Support backup data state computation

Entity data is computed with CRC32 checksum and saved to state file automatically.

Bug: 325144964
Test: Manual tests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:3455f82a21f8d6ce68641748149f2cdd38fa837b)
Merged-In: Ib74178fa87c1a11c39a703f6be409b33da00a00e
Change-Id: Ib74178fa87c1a11c39a703f6be409b33da00a00e