Always collect stack traces for WTF-level ProtoLog messages

This change ensures that a stack trace is always captured in Perfetto
traces for ProtoLog messages logged at the WTF level, regardless of
whether stack trace collection is enabled for the specific ProtoLog
group.

This will make it easier to identify the root cause of WTF log messages
in Pitot from field traces.

Flag: EXEMPT minor change
Bug: 438657912
Change-Id: I954d6ef64a5dbf391b87b12fe01f65f23943327e