Add API's for managing bucket quota (#9379)

This PR allows setting a "hard" or "fifo" quota
restriction at the bucket level. Buckets that
have reached the FIFO quota configured, will
automatically be cleaned up in FIFO manner until
bucket usage drops to configured quota.
If a bucket is configured with a "hard" quota
ceiling, all further writes are disallowed.

cmd/disk-cache-backend.go

@@ -245,7 +245,7 @@ func (c *diskCache) purge(ctx context.Context) {
 	// need to be cleaned up.
 	expiry := UTCNow().Add(-cacheExpiryDays)
 	// defaulting max hits count to 100
-	scorer, err := newFileScorer(int64(toFree), time.Now().Unix(), 100)
+	scorer, err := newFileScorer(toFree, time.Now().Unix(), 100)
 	if err != nil {
 		logger.LogIf(ctx, err)
 		return