Query and session metrics repository support in new DCS multi-threaded server

Currently query and session metrics are stored in the Trafodion repository by MXOSRVR. The upcoming new DCS multi-threaded (MT) server will need to support writing the metrics to the this repository once it is functional and eventually replaces MXOSRVR. This involves moving the code relating to metrics gathering and writing to repository from MXOSRVR to the new MT server. This can be further expanded in the future to write the metrics other than the repository tables for e.g. a Kafka client etc.