Add a new column before creating rename triggers

What does this MR do?

When renaming a column concurrently, create the new column before creating the trigger.

MySQL doesn't allow us to create a trigger for a column that doesn't exist yet. Failing with this error:

Mysql2::Error: Unknown column 'build_events' in 'NEW': CREATE TRIGGER trigger_6a80c097c862_insert
BEFORE INSERT
ON `services`
FOR EACH ROW
SET NEW.`build_events` = NEW.`job_events`

Creating the new column before creating the trigger avoids this.

I encountered this in !11287 (merged), causing these failures:

• https://gitlab.com/gitlab-org/gitlab-ce/builds/16083000
• https://gitlab.com/gitlab-org/gitlab-ce/builds/16083002

These changes are already in that MR, to confirm they solve everything. Only tried them out locally.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together