[DISCUSS] Change the IA for MutableSizeHistogram and MutableTimeHistogram to LImitedPrivate

[Rushabh Shah]

Hi,
Currently the IA for MutableSizeHistogram and MutableTimeHistogram is
private. We want to use these classes in PHOENIX project and I thought we
can leverage the existing implementation from hbase histo implementation.
IIUC the private IA can't be used in other projects. Proposing to make it
LimitedPrivate and mark HBaseInterfaceAudience.PHOENIX. Please suggest.
Related jira: https://issues.apache.org/jira/browse/HBASE-24520