Unified Storage: Add SQL template package (#87524)

* added sqltemplate package

* addded example

* fix linting issues

* improve code readability

* fix documentation

pkg/services/store/entity/sqlstash/sqltemplate/args.go

@@ -0,0 +1,14 @@
+package sqltemplate
+
+// Args keeps the data that needs to be passed to the engine for execution in
+// the right order. Add it to your data types passed to SQLTemplate, either by
+// embedding or with a named struct field if its Arg method would clash with
+// another struct field.
+type Args []any
+
+// Arg can be called from within templates to pass arguments to the SQL driver
+// to use in the execution of the query.
+func (a *Args) Arg(x any) string {
+	*a = append(*a, x)
+	return "?"
+}