Improve rate limiting through ABFS in Manifest Committer

I need a load test to verify that the rename resilience of the manifest committer actually works as intended

• test suite with name ILoadTest* prefix (as with s3)
• parallel test running with many threads doing many renames
• verify that rename recovery should be detected
• and that all renames MUST NOT fail.

maybe also: metrics for this in fs and doc update.
Possibly; LogExactlyOnce to warn of load issues