Renames a few metrics for consistency with the logs processing module.
This CL changes the names of several metrics to be consistent with what
we use for the logs parsing module. E.g. for metrics consistency,
CdmSecurityLevel is referred to as "security_level" and SecurityLevel
is referred to as "requested_security_level".
The GetSecurityLevel method was modified to use CdmSecurityLevel instead
of the previous string type.
This CL is a merge from wvgerrit/28423
BUG: 37627621
BUG: 37627483
Test: Updated and ran unit tests to verify no regressions.
Change-Id: Ia4a8b202325386f2e02dcda4f58010dd7957a048
80a95a1b64