Trim unnecessary data from CpuWakeupStats

Unsupported wakeups, like aborts, were taking up unnecessary memory as
Wakeup objects.
Also removed the raw reason string which would be redundant after it was
successfully parsed into components.

Also added some unit tests exercising CPU_WAKEUP_SUBSYSTEM_WIFI.

Test: atest FrameworksServicesTests:CpuWakeupStatsTest

Bug: 271216325
Change-Id: I7fb678586b581e380ddc0361028a0e23c653dd14