Support limiting stats number per scope

[TAOXUY]

Commit Message: add support for limiting the max number of stats(counter/gauge/histogram) per scope. This helps with memory explosion caused by high cardinality stats. Risk Level: low Testing: unit test covered Docs Changes: no doc update as it is a library support for internal usage Release Notes: updated Platform Specific Features: no

[TAOXUY]

@kyessenov

[adisuissa]

Assigning @kyessenov for a first-pass review. /assign @kyessenov

[TAOXUY]

/retest

[phlax]

@TAOXUY needs main merge

@kyessenov i think this is awaiting further review

[kyessenov]

Sorry for the delay. Jason is on my team, and we chat offline about it. /wait