Share available TAGs with other processes via IPC.

Other apps like system ui may want to start custom traces, but they
don't have access to the perfetto commands that retrieve available tags
due to SELinux constraints. This change creates an API for other apps to
retrieve that data.

Bug: 305049544
Test: Verified via logs that tags are returned from the service
correctly.
Flag: com.android.systemui.record_issue_qs_tile

Change-Id: I06cd2986a6affebc02600c37ef707a96719d14b6