Allow multiple projects per issue and pull requests (#36784)

Add ability to add and remove multiple projects per issue
and pull request.

Resolve #12974

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Signed-off-by: Icy Avocado <avocado@ovacoda.com>
Co-authored-by: Tyrone Yeh <siryeh@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: OpenCode (gpt-5.2-codex) <opencode@openai.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.7) <noreply@anthropic.com>

options/locale/locale_en-US.json

@@ -1385,6 +1385,7 @@
   "repo.projects.column.delete": "Delete Column",
   "repo.projects.column.deletion_desc": "Deleting a project column moves all related issues to the default column. Continue?",
   "repo.projects.column.color": "Color",
+  "repo.projects.column": "Column",
   "repo.projects.open": "Open",
   "repo.projects.close": "Close",
   "repo.projects.column.assigned_to": "Assigned to",