cached diskIDs are not needed for scanner healing (#14170)

This PR removes an unnecessary state that gets
passed around for DiskIDs, which is not necessary
since each disk exactly knows which pool and which
set it belongs to on a running system.

Currently cached DiskId's won't work properly
because it always ends up skipping offline disks
and never runs healing when disks are offline, as
it expects all the cached diskIDs to be present
always. This also sort of made things in-flexible
in terms perhaps a new diskID for `format.json`.
(however this is not a big issue)

This is an unnecessary requirement that healing
via scanner needs all drives to be online, instead
healing should trigger even when partial nodes
and drives are available this ensures that we
keep the SLA in-tact on the objects when disks
are offline for a prolonged period of time.

cmd/erasure.go

@@ -357,23 +357,6 @@ func (er erasureObjects) nsScanner(ctx context.Context, buckets []BucketInfo, bf
 		return nil
 	}
 
-	// Collect disks for healing.
-	allDisks := er.getDisks()
-	allDiskIDs := make([]string, 0, len(allDisks))
-	for _, disk := range allDisks {
-		if disk == OfflineDisk {
-			// its possible that disk is OfflineDisk
-			continue
-		}
-		id, _ := disk.GetDiskID()
-		if id == "" {
-			// its possible that disk is unformatted
-			// or just went offline
-			continue
-		}
-		allDiskIDs = append(allDiskIDs, id)
-	}
-
 	// Load bucket totals
 	oldCache := dataUsageCache{}
 	if err := oldCache.load(ctx, er, dataUsageCacheName); err != nil {
@@ -479,7 +462,6 @@ func (er erasureObjects) nsScanner(ctx context.Context, buckets []BucketInfo, bf
 				}
 				cache.Info.BloomFilter = bloom
 				cache.Info.SkipHealing = healing
-				cache.Disks = allDiskIDs
 				cache.Info.NextCycle = wantCycle
 				if cache.Info.Name != bucket.Name {
 					logger.LogIf(ctx, fmt.Errorf("cache name mismatch: %s != %s", cache.Info.Name, bucket.Name))