For a egionserver's view of a table (the regions
that belong to a table hosted on a regionserver),
this change tracks the latencies of operations that
affect the regions for this table.
Tracking at the per-table level avoids the memory bloat
and performance impact that accompanied the previous
per-region latency metrics while still providing important
details for operators to consume.
Signed-Off-By: Andrew Purtell <apurtell@apache.org>