Removed all jQuery AJAX calls and replaced with our fetch wrapper.
Tested the following functionalities and they work as before:
- column creation
- column deletion
- issue movement between columns
- column reordering
- column edit
- default column changing
# Demo using `fetch` instead of jQuery AJAX
![demo](https://github.com/go-gitea/gitea/assets/20454870/99e6898f-baa3-462c-acec-46a910874dbe)
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Signed-off-by: Yarden Shoham <git@yardenshoham.com>
(cherry picked from commit 397997093870226dafb70c4a3133f2ebe0fe3e2c)