Add a hidden API to set trace tag on atrace counters.

Currently the only counter API on trace uses the APP tag. Add a new
(hidden) API that will allow the system to set counters with different
tags.

Bug: 358369221
Flag: EXEMPT - adding hidden API only with no usage yet
Test: Try to add a counter with TRACE_TAG_WINDOW_MANAGER and check trace
Change-Id: I874d60998a26b7a80ac93b0a5e70ffddcaa9197c