Alerting: Refactor ruleRoutine to take an entire ruleInfo instance (#83858)

* Make stop a real method

* ruleRoutine takes a ruleInfo reference directly rather than pieces of it

* Fix whitespace

pkg/services/ngalert/schedule/alert_rule.go

@@ -10,12 +10,17 @@ type alertRuleInfo struct {
 	evalCh   chan *evaluation
 	updateCh chan ruleVersionAndPauseStatus
 	ctx      context.Context
-	stop     func(reason error)
+	stopFn   util.CancelCauseFunc
 }
 
 func newAlertRuleInfo(parent context.Context) *alertRuleInfo {
 	ctx, stop := util.WithCancelCause(parent)
-	return &alertRuleInfo{evalCh: make(chan *evaluation), updateCh: make(chan ruleVersionAndPauseStatus), ctx: ctx, stop: stop}
+	return &alertRuleInfo{
+		evalCh:   make(chan *evaluation),
+		updateCh: make(chan ruleVersionAndPauseStatus),
+		ctx:      ctx,
+		stopFn:   stop,
+	}
 }
 
 // eval signals the rule evaluation routine to perform the evaluation of the rule. Does nothing if the loop is stopped.
@@ -58,3 +63,8 @@ func (a *alertRuleInfo) update(lastVersion ruleVersionAndPauseStatus) bool {
 		return false
 	}
 }
+
+// stop sends an instruction to the rule evaluation routine to shut down. an optional shutdown reason can be given.
+func (a *alertRuleInfo) stop(reason error) {
+	a.stopFn(reason)
+}