CBG-4734: fix for race when removing a value that is being loaded into rev cache

[gregns1]

CBG-4734

Added a new function to remove only from rev lookup and have extra logic around eviction to enure we are evicting values we should be

Pre-review checklist

• Removed debug logging (fmt.Print, log.Print, ...)
• Logging sensitive data? Make sure it's tagged (e.g. base.UD(docID), base.MD(dbName))
• Updated relevant information in the API specifications (such as endpoint descriptions, schemas, ...) in docs/api

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGateway-Integration/3235/

[Copilot]

Pull Request Overview

This pull request fixes a race condition in the revision cache where an item being evicted could still be in the process of loading from the bucket. The solution adds retry loops that wait for the canEvict atomic boolean to be true before proceeding with cache removal operations.

• Adds retry loops in both removeFromCacheByCV and removeFromCacheByRev methods to wait for items to finish loading
• Uses atomic boolean check on elem.canEvict to determine when it's safe to evict an item

[bbrks]

LGTM