The key change is to revamp how we parse/store/match a log event, especially how we match repeated
field and attribution nodes, and how we construct dimensions and compare them.
+ We use a integer to encode the field of a log element. And also encode the FieldMatcher into an
integer and a bit mask. The log matching becomes 2 integer operations.
+ Dimension is stored as encoded field and value pair. Checking if 2 dimensions are equal is then
becoming checking if the underlying integers are equal. The integers are stored contiguously
in memory, so it's much faster than previous tree structure.
Start review from FieldValue.h
Test: statsd_test + new unit tests
Bug: 72659059
Change-Id: Iec8daeacdd3f39ab297c10ab9cd7b710a9c42e86
8a8d16ceea