Use auto-updating, natively hoverable, localized time elements (#23988)

- Added [GitHub's `relative-time` element](https://github.com/github/relative-time-element)
- Converted all formatted timestamps to use this element
- No more flashes of unstyled content around time elements
- These elements are localized using the `lang` property of the HTML file
- Relative (e.g. the activities in the dashboard) and duration (e.g.
server uptime in the admin page) time elements are auto-updated to keep
up with the current time without refreshing the page
- Code that is not needed anymore such as `formatting.js` and parts of `since.go` have been deleted

Replaces #21440
Follows #22861

## Screenshots

### Localized

![image](https://user-images.githubusercontent.com/20454870/230775041-f0af4fda-8f6b-46d3-b8e3-d340c791a50c.png)

![image](https://user-images.githubusercontent.com/20454870/230673393-931415a9-5729-4ac3-9a89-c0fb5fbeeeb7.png)

### Tooltips

#### Native for dates

![image](https://user-images.githubusercontent.com/20454870/230797525-1fa0a854-83e3-484c-9da5-9425ab6528a3.png)

#### Interactive for relative

![image](https://user-images.githubusercontent.com/115237/230796860-51e1d640-c820-4a34-ba2e-39087020626a.png)

### Auto-update

![rec](https://user-images.githubusercontent.com/20454870/230672159-37480d8f-435a-43e9-a2b0-44073351c805.gif)

---------

Signed-off-by: Yarden Shoham <git@yardenshoham.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: delvh <dev.lh@web.de>

package-lock.json

@@ -13,6 +13,7 @@
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         "@claviska/jquery-minicolors": "2.3.6",
         "@github/markdown-toolbar-element": "2.1.1",
+        "@github/relative-time-element": "4.2.4",
         "@github/text-expander-element": "2.3.0",
         "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
         "@primer/octicons": "18.3.0",
@@ -851,6 +852,11 @@
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     },
+    "node_modules/@github/relative-time-element": {
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+      "resolved": "https://registry.npmjs.org/@github/relative-time-element/-/relative-time-element-4.2.4.tgz",
+      "integrity": "sha512-18qgH9FYUHYN9K3z4s35auDHww1dKTU6TacI8JkA5OuvHVa1lTMuSTZ4hIoJngD5+mizcoRMOs6p/yZYMIjsyg=="
+    },
     "node_modules/@github/text-expander-element": {
       "version": "2.3.0",
       "resolved": "https://registry.npmjs.org/@github/text-expander-element/-/text-expander-element-2.3.0.tgz",