Revert^2 "trace-ipc: Don't hold procLock while calling out."

This reverts commit 2caf6f9f.

Dumping IPC transactions can be a long running operation; instead of
holding the procLock for all of it, make a copy of the list of
processes, and iterate over those instead.

Bug: 306025653
Change-Id: I4affb7e63c6c597823694a91db6678e358960dc4
Flag: EXEMPT bugfix
Test: adb shell am trace-ipc start / stop