Add MaxNoncurrentVersions to NoncurrentExpiration action (#13580)

This unit allows users to limit the maximum number of noncurrent 
versions of an object.

To enable this rule you need the following *ilm.json*
```
cat >> ilm.json <<EOF
{
    "Rules": [
        {
            "ID": "test-max-noncurrent",
            "Status": "Enabled",
            "Filter": {
                "Prefix": "user-uploads/"
            },
            "NoncurrentVersionExpiration": {
                "MaxNoncurrentVersions": 5
            }
        }
    ]
}
EOF
mc ilm import myminio/mybucket < ilm.json
```

internal/bucket/lifecycle/lifecycle.go

@@ -29,10 +29,11 @@ import (
 )
 
 var (
-	errLifecycleTooManyRules = Errorf("Lifecycle configuration allows a maximum of 1000 rules")
-	errLifecycleNoRule       = Errorf("Lifecycle configuration should have at least one rule")
-	errLifecycleDuplicateID  = Errorf("Lifecycle configuration has rule with the same ID. Rule ID must be unique.")
-	errXMLNotWellFormed      = Errorf("The XML you provided was not well-formed or did not validate against our published schema")
+	errLifecycleTooManyRules                = Errorf("Lifecycle configuration allows a maximum of 1000 rules")
+	errLifecycleNoRule                      = Errorf("Lifecycle configuration should have at least one rule")
+	errLifecycleDuplicateID                 = Errorf("Lifecycle configuration has rule with the same ID. Rule ID must be unique.")
+	errXMLNotWellFormed                     = Errorf("The XML you provided was not well-formed or did not validate against our published schema")
+	errLifecycleInvalidNoncurrentExpiration = Errorf("Exactly one of NoncurrentDays (positive integer) or MaxNoncurrentVersions should be specified in a NoncurrentExpiration rule.")
 )
 
 const (
@@ -140,6 +141,9 @@ func (lc Lifecycle) HasActiveRules(prefix string, recursive bool) bool {
 		if rule.NoncurrentVersionExpiration.NoncurrentDays > 0 {
 			return true
 		}
+		if rule.NoncurrentVersionExpiration.MaxNoncurrentVersions > 0 {
+			return true
+		}
 		if !rule.NoncurrentVersionTransition.IsNull() {
 			return true
 		}
@@ -234,6 +238,10 @@ func (lc Lifecycle) FilterActionableRules(obj ObjectOpts) []Rule {
 			rules = append(rules, rule)
 			continue
 		}
+		if rule.NoncurrentVersionExpiration.MaxNoncurrentVersions > 0 {
+			rules = append(rules, rule)
+			continue
+		}
 		// The NoncurrentVersionTransition action requests MinIO to transition
 		// noncurrent versions of objects x days after the objects become
 		// noncurrent.
@@ -468,3 +476,32 @@ func (lc Lifecycle) TransitionTier(obj ObjectOpts) string {
 	}
 	return ""
 }
+
+// NoncurrentVersionsExpirationLimit returns the minimum limit on number of
+// noncurrent versions across rules.
+func (lc Lifecycle) NoncurrentVersionsExpirationLimit(obj ObjectOpts) int {
+	var lim int
+	for _, rule := range lc.FilterActionableRules(obj) {
+		if rule.NoncurrentVersionExpiration.MaxNoncurrentVersions == 0 {
+			continue
+		}
+		if lim == 0 || lim > rule.NoncurrentVersionExpiration.MaxNoncurrentVersions {
+			lim = rule.NoncurrentVersionExpiration.MaxNoncurrentVersions
+		}
+	}
+	return lim
+}
+
+// HasMaxNoncurrentVersions returns true if there exists a rule with
+// MaxNoncurrentVersions limit set.
+func (lc Lifecycle) HasMaxNoncurrentVersions() bool {
+	for _, rule := range lc.Rules {
+		if rule.Status == Disabled {
+			continue
+		}
+		if rule.NoncurrentVersionExpiration.MaxNoncurrentVersions > 0 {
+			return true
+		}
+	}
+	return false
+}