client lib: Add a DCHECK to ThreadTracks for tid != 0
client lib: Add a DCHECK to ThreadTracks for tid != 0

tid 0 is invalid, but if accidentally passed to ThreadTrack's
constructor, it would create a reference to a thread track with the
same uuid as the corresponding process track.

Change-Id: I920cf760e12e2658a2219282b44854d4be0803c3

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto