[MS82.2] Add a rewriteSingle method that takes two timestamps

This CL provides a public method in FileRotator to
allow caller to write data to a specified standalone file.

This CL also fix a file name generatign error in platform
tools.

Test: NetworkStatsServiceTest NetworkStatsCollectionTest
Bug: 230289468
Change-Id: I17558f349cb2a33062972fe1af96a19356798692
Merged-In: I17558f349cb2a33062972fe1af96a19356798692
  (pure cherry-picked from ag/18408306)