Refactor to support multiple files per trace in Winscope

This is required because when tracing transasction merges each process where the merge occurs is responsible for recording this and dumping this information. So in addition to the current transaction file, the transactions trace may contains many additional files.

Test: Try and run through all usecases of the app and make sure everything still works
Change-Id: Iba66536fb413a1875847ec673616da20e94d5feb
26 files changed