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/less/_base.less

@@ -1924,10 +1924,6 @@ footer {
   display: block;
 }
 
-[v-cloak] {
-  display: none !important;
-}
-
 .repos-search {
   padding-bottom: 0 !important;
 }

web_src/less/_repository.less

@@ -222,12 +222,6 @@
       font-size: 1.2em;
     }
 
-    .choose.reference {
-      .header .icon {
-        font-size: 1.4em;
-      }
-    }
-
     .repo-path {
 
       .section,