Support new transactions trace

Keep previous implementation as "transactions (legacy)"

The proxy is not yet able to generate traces because no
adb command is available at the moment.

Known issues:
- Enum fields are not translated into values in Winscope
  (only IntDef support)

Prepare the codebase for the new SF transaction tracing
Bug: 167521734
Test: run winscope and collect a transactions trace

Change-Id: Ie489ee1a63056377c1699e14df8de975c2978085
17 files changed