feat: use go:embed to embed templates (#1756)

tools/goctl/api/tsgen/gencomponents.go

@@ -1,6 +1,7 @@
 package tsgen
 
 import (
+	_ "embed"
 	"path"
 	"strings"
 	"text/template"
@@ -10,12 +11,8 @@ import (
 	"github.com/zeromicro/go-zero/tools/goctl/util/pathx"
 )
 
-const (
-	componentsTemplate = `// Code generated by goctl. DO NOT EDIT.
-
-{{.componentTypes}}
-`
-)
+//go:embed components.tpl
+var componentsTemplate string
 
 func genComponents(dir string, api *spec.ApiSpec) error {
 	types := api.Types