Make Table/Keyspace Metric Names Consistent With Each Other

As part of CASSANDRA-15821 it became apparent that certain metric names found in keyspace and tables had different names but were in fact the same metric - they are as follows:

• Table.SyncTime == Keyspace.RepairSyncTime
• Table.RepairedDataTrackingOverreadRows == Keyspace.RepairedOverreadRows
• Table.RepairedDataTrackingOverreadTime == Keyspace.RepairedOverreadTime
• Table.AllMemtablesHeapSize == Keyspace.AllMemtablesOnHeapDataSize
• Table.AllMemtablesOffHeapSize == Keyspace.AllMemtablesOffHeapDataSize
• Table.MemtableOnHeapSize == Keyspace.MemtableOnHeapDataSize
• Table.MemtableOffHeapSize == Keyspace.MemtableOffHeapDataSize

Also, client metrics are the only metrics to start with a lower case letter. Change those to upper case to match all the other metrics.

Unifying this naming would help make metrics more consistent as part of CASSANDRA-15582