Allow to specify custom track name in LogBuffer

This allows to use custom track names for each logbuffer.

As part of this cl, also NotifiactionsLog Logbuffers are all grouped under a "Notification pipeline" track group in perfetto traces (only for the ones that were already in systrace)

+ add a check for Trace.isEnabled before generating the concatenated string in LogBuffer.echoToSystrace

Bug: 362719719
Bug: 337016334
Test: Perfetto trace
Flag: NONE - tracing change
Change-Id: I2d0375ac275c980b63fd02c6ec0df3ba9847b849