Add <overflow-menu>, rename webcomponents (#29400)

1. Add `<overflow-menu>` web component
2. Rename `<gitea-origin-url>` to `<origin-url>` and make filenames
match.

<img width="439" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/2fbe4ca4-110b-4ad2-8e17-c1e116ccbd74">

<img width="444" alt="Screenshot 2024-03-02 at 21 36 52"
src="https://github.com/go-gitea/gitea/assets/115237/aa8f786e-dc8c-4030-b12d-7cfb74bdfd6e">

<img width="537" alt="Screenshot 2024-03-03 at 03 05 06"
src="https://github.com/go-gitea/gitea/assets/115237/fddd50aa-adf1-4b4b-bd7f-caf30c7b2245">


![image](https://github.com/go-gitea/gitea/assets/115237/0f43770c-834c-4a05-8e3d-d30eb8653786)


![image](https://github.com/go-gitea/gitea/assets/115237/4b4c6bd7-843f-4f49-808f-6b3aed5e9f9a)

TODO:

- [x] Check if removal of `requestAnimationFrame` is possible to avoid
flash of content. Likely needs a `MutationObserver`.
- [x] Hide tippy when button is removed from DOM.
- [x] ~~Implement right-aligned items
(https://github.com/go-gitea/gitea/pull/28976)~~. Not going to do it.
- [x] Clean up CSS so base element has no background and add background
via tailwind instead.
- [x] Use it for org and user page.

---------

Co-authored-by: Giteabot <teabot@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/repo/issue/view_content/pull_merge_instruction.tmpl

@@ -8,7 +8,7 @@
 	{{end}}
 	<div class="ui secondary segment">
 		{{if eq .PullRequest.Flow 0}}
-		<div>git fetch -u {{if ne .PullRequest.HeadRepo.ID .PullRequest.BaseRepo.ID}}<gitea-origin-url data-url="{{.PullRequest.HeadRepo.Link}}"></gitea-origin-url>{{else}}origin{{end}} {{.PullRequest.HeadBranch}}:{{$localBranch}}</div>
+		<div>git fetch -u {{if ne .PullRequest.HeadRepo.ID .PullRequest.BaseRepo.ID}}<origin-url data-url="{{.PullRequest.HeadRepo.Link}}"></origin-url>{{else}}origin{{end}} {{.PullRequest.HeadBranch}}:{{$localBranch}}</div>
 		<div>git checkout {{$localBranch}}</div>
 		{{else}}
 		<div>git fetch -u origin {{.GetGitRefName}}:{{$localBranch}}</div>