base/trace_event: Remove id mangling

Remove the deprecated trace id mangling facility and convert the last
remaining uses to the new API as follows:

  TRACE_ID_MANGLE()       =>  TRACE_ID_LOCAL()   // Process-local id.
  TRACE_ID_DONT_MANGLE()  =>  TRACE_ID_GLOBAL()  // Cross-process id.

Test: Checked that a trace with input flow events still looks correct.
Bug: 639003
Change-Id: I2493e89787a49368528f844e8d37cfd120558fb0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2016648
Commit-Queue: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Auto-Submit: Sami Kyöstilä <skyostil@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#736109}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: e04ca1bdc3d9a2621448869d20c298301d91e456