[cross-repo] Add 'timestampMillis' to Stats-based classes
[cross-repo] Add 'timestampMillis' to Stats-based classes

Similar to https://github.com/Kurento/kms-
core/commit/6e81ec26964b4f9b17de1eb2f5eb55417e3c88fb
We're adding finer precision timestamps to the Stats class and all its
sub-classes.

Kurento/kurento-module-creator,Kurento/kurento-module-creator