Use graceful editorconfig loader to reduce errors when loading malformed editorconfigs (#21257)

The _graceful_ should fail less when the `.editorconfig` file isn't
properly written, e.g. boolean values from YAML or unparseable numbers
(when a number is expected). As is... information is lost as the
_warning_ (a go-multierror.Error) is ignored. If anybody knows how to
send them to the UI as warning; any help is appreciated.

Closes #20694

Signed-off-by: Yoan Blanc <yoan@dosimple.ch>

routers/api/v1/repo/file.go

@@ -381,7 +381,7 @@ func GetEditorconfig(ctx *context.APIContext) {
 	//   "404":
 	//     "$ref": "#/responses/notFound"
 
-	ec, err := ctx.Repo.GetEditorconfig(ctx.Repo.Commit)
+	ec, _, err := ctx.Repo.GetEditorconfig(ctx.Repo.Commit)
 	if err != nil {
 		if git.IsErrNotExist(err) {
 			ctx.NotFound(err)