Add initial support for bucket lifecycle (#7563)

This PR is based off @sinhaashish's PR for object lifecycle
management, which includes support only for,
- Expiration of object
- Filter using object prefix (_not_ object tags)

N B the code for actual expiration of objects will be included in a
subsequent PR.

cmd/globals.go

@@ -83,6 +83,11 @@ const (
 	// GlobalMultipartCleanupInterval - Cleanup interval when the stale multipart cleanup is initiated.
 	GlobalMultipartCleanupInterval = time.Hour * 24 // 24 hrs.
 
+	// GlobalServiceExecutionInterval - Executes the Lifecycle events.
+	GlobalServiceExecutionInterval = time.Hour * 24 // 24 hrs.
+
+	// Refresh interval to update in-memory bucket lifecycle cache.
+	globalRefreshBucketLifecycleInterval = 5 * time.Minute
 	// Refresh interval to update in-memory iam config cache.
 	globalRefreshIAMInterval = 5 * time.Minute
 
@@ -148,6 +153,8 @@ var (
 	globalPolicySys       *PolicySys
 	globalIAMSys          *IAMSys
 
+	globalLifecycleSys *LifecycleSys
+
 	// CA root certificates, a nil value means system certs pool will be used
 	globalRootCAs *x509.CertPool