Refactor branch/tag selector to Vue SFC (#23421)

Follow #23394

There were many bad smells in old code. This PR only moves the code into
Vue SFC, doesn't touch the unrelated logic.

update: after
5f23218c85
, there should be no usage of the vue-rumtime-compiler anymore
(hopefully), so I think this PR could close #19851

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/js/utils/url.test.js

@@ -0,0 +1,7 @@
+import {expect, test} from 'vitest';
+import {pathEscapeSegments} from './url.js';
+
+test('pathEscapeSegments', () => {
+  expect(pathEscapeSegments('a/b/c')).toEqual('a/b/c');
+  expect(pathEscapeSegments('a/b/ c')).toEqual('a/b/%20c');
+});