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>

routers/web/repo/pull.go

@@ -1329,14 +1329,12 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 		return
 	}
 
-	if projectID > 0 {
-		if !ctx.Repo.CanWrite(unit.TypeProjects) {
-			ctx.Error(http.StatusBadRequest, "user hasn't the permission to write to projects")
-			return
-		}
-		if err := issues_model.ChangeProjectAssign(ctx, pullIssue, ctx.Doer, projectID); err != nil {
-			ctx.ServerError("ChangeProjectAssign", err)
-			return
+	if projectID > 0 && ctx.Repo.CanWrite(unit.TypeProjects) {
+		if err := issues_model.IssueAssignOrRemoveProject(ctx, pullIssue, ctx.Doer, projectID, 0); err != nil {
+			if !errors.Is(err, util.ErrPermissionDenied) {
+				ctx.ServerError("IssueAssignOrRemoveProject", err)
+				return
+			}
 		}
 	}