RS: v2 Prometheus metrics (#540)

* DOC-3945 v2 DB Prometheus metrics

* Remove list-formatted metrics preview

* DOC-3946 v2 node Prometheus metrics

* DOC-3949 v2 cluster Prometheus metrics

* DOC-3950 v2 proxy Prometheus metrics

* DOC-3947 v2 replication Prometheus metrics

* DOC-3948 v2 shard Prometheus metrics

* Small copy edits and fixes

* More small copy edits and fixes

* Change v2 not supported messages to N/A in tables

* DOC-4071 Separate v2 Prometheus metrics and transition tables

* DOC-3552 Cluster watchdog Prometheus metrics

* DOC-3944 Placeholder - plan to provide v2 metric names when available instead of PromQL on dedicated v2 metrics page

* Table formatting

* DOC-4294 Add latency histogram metrics to v2 Prometheus metrics

* Remove PromQL from dedicated v2 metrics page

* DOC-4294 Moved example PromQL for latency histogram metrics to description column

* DOC-4417 RS: Update v2 cert metric with new name

* DOC-3944 Feedback update to remove a few v2 metrics

* Update RS version to 7.8.2

* DOC-3944 Feedback updates for v2 metrics

* DOC-3944 Feedback update for title of v1 to v2 metrics transition doc

* DOC-3944 Add v2 replication metrics

* DOC-3944 Add v2 DB metrics

* DOC-3944 Change v2 metric column name

Author: rrelledge