feat(repo): add quick repository switcher to repo header (#38188)

Add a GitHub-style quick repo switcher: a caret next to the owner/repo
breadcrumb
opens a dropdown that lists and searches the current owner's
repositories and
navigates to the selected one. The current repository is marked with a
check, and
private/fork repos show an icon.

Also, fix various bugs in fomtantic dropdown remote query

## Screenshots

<img width="505" height="198" alt="image"
src="https://github.com/user-attachments/assets/9f673d1b-fe60-41f0-b9e2-b00dc43720b5"
/>

Fixes #38187

---------

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

web_src/js/features/repo-issue.ts

@@ -303,8 +303,6 @@ export function initRepoIssueReferenceIssue() {
   fomanticQuery(elDropdown).dropdown({
     fullTextSearch: true,
     apiSettings: {
-      cache: false,
-      rawResponse: true,
       url: `${appSubUrl}/repo/search?q={query}&limit=20`,
       onResponse(response: any) {
         const filteredResponse = {success: true, results: [] as Array<Record<string, any>>};