AlertingNG: base API implementation (#31824)

* AlertingNG: base API implementation

* Pass the interface instead of the base impl

* Ruler mock draft (WIP)

* Update alerting-api dependency

* Improve mock implementation

pkg/services/ngalert/api/util.go

@@ -0,0 +1,15 @@
+package api
+
+import (
+	"fmt"
+	"regexp"
+)
+
+var searchRegex = regexp.MustCompile(`\{(\w+)\}`)
+
+func toMacaronPath(path string) string {
+	return string(searchRegex.ReplaceAllFunc([]byte(path), func(s []byte) []byte {
+		m := string(s[1 : len(s)-1])
+		return []byte(fmt.Sprintf(":%s", m))
+	}))
+}