kv: introduce a rate limiter for the range consistency checker

Jesse Seldess (jseldess) commented:

PR: https://github.com/cockroachdb/cockroach/pull/49763

From release notes:
> Introduced a new flag named `server.consistency_check.max_rate` expressed in bytes/second to throttle the rate at which CockroachDB scans through the disk to perform a consistency check. This control is necessary to ensure smooth performance on a cluster with large node sizes (i.e. in the 10TB+ range) [#49763][#49763] {% comment %}doc{% endcomment %}

Jira Issue: DOC-611