Add support for bucket encryption feature (#8890)

- pkg/bucket/encryption provides support for handling bucket 
  encryption configuration
- changes under cmd/ provide support for AES256 algorithm only

Co-Authored-By: Poorna  <poornas@users.noreply.github.com>
Co-authored-by: Harshavardhana <harsha@minio.io>

cmd/server-main.go

@@ -159,6 +159,9 @@ func newAllSubsystems() {
 
 	// Create new lifecycle system.
 	globalLifecycleSys = NewLifecycleSys()
+
+	// Create new bucket encryption subsystem
+	globalBucketSSEConfigSys = NewBucketSSEConfigSys()
 }
 
 func initSafeMode(buckets []BucketInfo) (err error) {
@@ -280,6 +283,10 @@ func initAllSubsystems(buckets []BucketInfo, newObject ObjectLayer) (err error)
 		return fmt.Errorf("Unable to initialize lifecycle system: %w", err)
 	}
 
+	// Initialize bucket encryption subsystem.
+	if err = globalBucketSSEConfigSys.Init(buckets, newObject); err != nil {
+		return fmt.Errorf("Unable to initialize bucket encryption subsystem: %w", err)
+	}
 	return nil
 }