lmkd: Isolate statslog related code from lmkd code

Move statsd related code out of lmkd.c to minimize ifdefs sprinkled around
the code and make it more maintainable.

Bug: 74119935
Test: lmkd_unit_test
Change-Id: Ib22f90fd380b9a31e09ab18ef16787bc07415ddf
Signed-off-by: Suren Baghdasaryan <surenb@google.com>