Alerting: Various fixes for the alerts endpoint (#33182)

A set of fixes for the GET alert and groups endpoints.

- First, is the fact that the default values where not being for the query params. I've introduced a new method in the Grafana context that allow us to do this.
- Second, is the fact that alerts were never being transitioned to active. To my surprise this is actually done by the inhibitor in the pipeline - if an alert is not muted, or inhibited then it's active.
- Third, I have added an integration test to cover for regressions.

Signed-off-by: Josue Abreu <josue@grafana.com>

pkg/models/context.go

@@ -78,3 +78,13 @@ func (ctx *ReqContext) HasHelpFlag(flag HelpFlags1) bool {
 func (ctx *ReqContext) TimeRequest(timer prometheus.Summary) {
 	ctx.Data["perfmon.timer"] = timer
 }
+
+// QueryBoolWithDefault extracts a value from the request query params and applies a bool default if not present.
+func (ctx *ReqContext) QueryBoolWithDefault(field string, d bool) bool {
+	f := ctx.Query(field)
+	if f == "" {
+		return d
+	}
+
+	return ctx.QueryBool(field)
+}