feat(ui): convert disable/enable workflow menu to JS-less dropdown (#10133)

* convert the dropdown (overflow menu) to the JS-less one
    * the "link" still relies on JS to make a POST, changing this is not in scope of this PR
    * fixed the weird behavior where opener changes it's color when hovering over the "link"
    * the bug where the script that refreshes the list once in a while closes an open dropdown is not fixed and is not in scope of this PR
* use border in the opener
    * it might not look as sleek but it is easier to see and better for the user to be able to understand that this is an active intractable element
* global dropdown improvements
    * add rounding rules for dropdowns with only one item - the first such case
    * add testing for rounding rules
    * added a devtest page to play with the dropdown component on

Preview

B: https://codeberg.org/forgejo/forgejo/attachments/1462cdda-71f5-45d0-a206-33bb17740cb8
A: https://codeberg.org/forgejo/forgejo/attachments/d3c265cb-6b77-40c8-9944-d9327f3bec65

B: https://codeberg.org/forgejo/forgejo/attachments/17f17c29-4dcd-4015-b5b9-6d438bd2eb0b
A: https://codeberg.org/forgejo/forgejo/attachments/d94e196c-725e-47de-b4de-ed97b148ceb6

B: https://codeberg.org/forgejo/forgejo/attachments/1813ded9-f619-47d9-bf15-ad4bcd3535ab
A: https://codeberg.org/forgejo/forgejo/attachments/09042e58-331e-414d-ac8f-0f1091033b7f

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10133
Reviewed-by: Otto <otto@codeberg.org>

web_src/css/modules/dropdown.css

@@ -107,6 +107,9 @@ details.dropdown > .content > ul {
   &:last-of-type > li:last-child {
     border-radius: 0 0 var(--border-radius) var(--border-radius);
   }
+  &:only-of-type > li:only-child {
+    border-radius: var(--border-radius);
+  }
 }
 
 /* General styling of list items */