Fix logging for sharded deployments

[AndrewChubatiuk]

fixes #2134

---

Summary by cubic

Fix incorrect scaling logs for sharded vmagent and vmanomaly. Logs now only emit when the shard count changes and correctly label upscaling vs downscaling.

• Bug Fixes
  • Sharded deployments: emit logs only on shard count changes; compute action from previous vs current counts; use explicit VMAgent/VMAnomaly names; avoid false downscale messages. Fixes wrong log "VMAgent shard downscaling from=2 to=2" #2134.

^{Written for commit e167c0e. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 5 files

[vrutkovs]

Maybe lets make it look like this:

	isUpscaling := false
	if prevCR.IsSharded() {
		isUpscaling = prevShardCount < shardCount
		if prevShardCount != shardCount {
			action := "downscaling"
			if isUpscaling {
				action = "upscaling"
			}
			logger.WithContext(ctx).Info(fmt.Sprintf("VMAgent shard %s from=%d to=%d", action, prevShardCount, shardCount))
		}
	}