* feat(plugin): enhanced collection filtering for volume balance
Replace wildcard matching with three collection filter modes:
- ALL_COLLECTIONS (default): treat all volumes as one pool
- EACH_COLLECTION: run detection separately per collection
- Regex pattern: filter volumes by matching collection names
The EACH_COLLECTION mode extracts distinct collections from metrics
and calls Detection() per collection, sharing the maxResults budget
and clusterInfo (with ActiveTopology) across all calls.
* address PR review: fix wildcard→regexp replacement, optimize EACH_COLLECTION
* address nitpick: fail fast on config errors (invalid regex)
Add configError type so invalid collection_filter regex returns
immediately instead of retrying across all masters with the same
bad config. Transient errors still retry.
* address review: constants, unbounded maxResults, wildcard compat
- Define collectionFilterAll/collectionFilterEach constants to
eliminate magic strings across handler and metrics code
- Fix EACH_COLLECTION budget loop to treat maxResults <= 0 as
unbounded, matching Detection's existing semantics
- Treat "*" as ALL_COLLECTIONS for backward compat with wildcard
* address review: nil guard in EACH_COLLECTION grouping loop
* remove useless descriptor string test
00ce1c6eba