Use frontend fetch for branch dropdown component (#25719)

- Send request to get branch/tag list, use loading icon when waiting for
response.
- Only fetch when the first time branch/tag list shows.
- For backend, removed assignment to `ctx.Data["Branches"]` and
`ctx.Data["Tags"]` from `context/repo.go` and passed these data wherever
needed.
- Changed some `v-if` to `v-show` and used native `svg` as mentioned in
https://github.com/go-gitea/gitea/pull/25719#issuecomment-1631712757 to
improve perfomance when there are a lot of branches.
- Places Used the dropdown component:

     Repo Home Page
    
<img width="1429" alt="Screen Shot 2023-07-06 at 12 17 51"
src="6accc7b6-8d37-4e88-ae1a-bd2b3b927ea0">

    Commits Page

<img width="1431" alt="Screen Shot 2023-07-06 at 12 18 34"
src="2d0bf306-d1e2-45a8-a784-bc424879f537">

    Specific commit -> operations -> cherry-pick
    
<img width="758" alt="Screen Shot 2023-07-06 at 12 23 28"
src="1e557948-3881-4e45-a625-8ef36d45ae2d">

    Release Page
    
<img width="1433" alt="Screen Shot 2023-07-06 at 12 25 05"
src="3ec82af1-15a4-4162-a50b-04a9502161bb">

- Demo


d45d266b-3eb0-465a-82f9-57f78dc5f9f3

- Note:

UI of dropdown menu could be improved in another PR as it should apply
to more dropdown menus.

Fix #14180

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/repo/setting/protected_branch.go

@@ -21,6 +21,7 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/web"
+	"code.gitea.io/gitea/routers/web/repo"
 	"code.gitea.io/gitea/services/forms"
 	pull_service "code.gitea.io/gitea/services/pull"
 	"code.gitea.io/gitea/services/repository"
@@ -44,6 +45,11 @@ func ProtectedBranchRules(ctx *context.Context) {
 	}
 	ctx.Data["ProtectedBranches"] = rules
 
+	repo.PrepareBranchList(ctx)
+	if ctx.Written() {
+		return
+	}
+
 	ctx.HTML(http.StatusOK, tplBranches)
 }
 
@@ -52,6 +58,11 @@ func SetDefaultBranchPost(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("repo.settings.branches.update_default_branch")
 	ctx.Data["PageIsSettingsBranches"] = true
 
+	repo.PrepareBranchList(ctx)
+	if ctx.Written() {
+		return
+	}
+
 	repo := ctx.Repo.Repository
 
 	switch ctx.FormString("action") {