slack 21.0: backport v22/v23 VTOrc improvements, part 3

[timvaillancourt]

Description

This backports more v22/v23 optimizations we rely on for VTOrc:

1. vtorc: add stats to shard locks and instance discovery vitessio/vitess#17977
2. Check consultopo loaded >=1 credentials w/-consul_auth_static_file vitessio/vitess#18152 (pre-backport - 50% approved upstream)

Related Issue(s)

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes