Fix various problems around projects board view (#30696)

# The problem
The previous implementation will start multiple POST requests from the
frontend when moving a column and another bug is moving the default
column will never be remembered in fact.

# What's changed

- [x] This PR will allow the default column to move to a non-first
position
- [x] And it also uses one request instead of multiple requests when
moving the columns
- [x] Use a star instead of a pin as the icon for setting the default
column action
- [x] Inserted new column will be append to the end
- [x] Fix #30701 the newly added issue will be append to the end of the
default column
- [x] Fix when deleting a column, all issues in it will be displayed
from UI but database records exist.
- [x] Add a limitation for columns in a project to 20. So the sorting
will not be overflow because it's int8.

---------

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

templates/projects/view.tmpl

@@ -64,7 +64,7 @@
 </div>
 
 <div id="project-board">
-	<div class="board {{if .CanWriteProjects}}sortable{{end}}">
+	<div class="board {{if .CanWriteProjects}}sortable{{end}}"{{if .CanWriteProjects}} data-url="{{$.Link}}/move"{{end}}>
 		{{range .Columns}}
 			<div class="ui segment project-column"{{if .Color}} style="background: {{.Color}} !important; color: {{ContrastColor .Color}} !important"{{end}} data-id="{{.ID}}" data-sorting="{{.Sorting}}" data-url="{{$.Link}}/{{.ID}}">
 				<div class="project-column-header{{if $canWriteProject}} tw-cursor-grab{{end}}">