Alerting: Emit warning when creating or updating unusually large groups (#82279)

* Add config for limit of rules per rule group

* Warn when editing big groups through normal API

* Warn on prov api writes for groups

* Wire up comp root, tests

* Also add warning to state manager warm

* Drop unnecessary conversion

pkg/setting/setting_unified_alerting.go

@@ -101,6 +101,7 @@ type UnifiedAlertingSettings struct {
 	// MaxStateSaveConcurrency controls the number of goroutines (per rule) that can save alert state in parallel.
 	MaxStateSaveConcurrency   int
 	StatePeriodicSaveInterval time.Duration
+	RulesPerRuleGroupLimit    int64
 }
 
 // RemoteAlertmanagerSettings contains the configuration needed
@@ -352,6 +353,9 @@ func (cfg *Cfg) ReadUnifiedAlertingSettings(iniFile *ini.File) error {
 		uaCfg.DefaultRuleEvaluationInterval = uaMinInterval
 	}
 
+	quotas := iniFile.Section("quota")
+	uaCfg.RulesPerRuleGroupLimit = quotas.Key("alerting_rule_group_rules").MustInt64(100)
+
 	remoteAlertmanager := iniFile.Section("remote.alertmanager")
 	uaCfgRemoteAM := RemoteAlertmanagerSettings{
 		Enable:   remoteAlertmanager.Key("enabled").MustBool(false),