Rename project board -> column to make the UI less confusing (#30170)

This PR split the `Board` into two parts. One is the struct has been
renamed to `Column` and the second we have a `Template Type`.

But to make it easier to review, this PR will not change the database
schemas, they are just renames. The database schema changes could be in
future PRs.

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: yp05327 <576951401@qq.com>

options/locale/locale_en-US.ini

@@ -1215,7 +1215,7 @@ branches = Branches
 tags = Tags
 issues = Issues
 pulls = Pull Requests
-project_board = Projects
+projects = Projects
 packages = Packages
 actions = Actions
 labels = Labels
@@ -1379,7 +1379,7 @@ ext_issues = Access to External Issues
 ext_issues.desc = Link to an external issue tracker.
 
 projects = Projects
-projects.desc = Manage issues and pulls in project boards.
+projects.desc = Manage issues and pulls in projects.
 projects.description = Description (optional)
 projects.description_placeholder = Description
 projects.create = Create Project