This commit has two migrations:

1. The first prunes duplicate rows in the project_features table and leaves
   the row with the highest ID.  Since the behavior was indeterministic before
   and depended on which row the database decided to use, this change at least
   makes the permissions consistent. For example, in some cases, the Wiki may
   have been disabled but enabled in another entry.

2. The second adds a non-null constraint on the project_features.project_id
   column.

Closes #37882

Fixes a significant part of gitlab-com/migration#408.

We found that we were overcounting Wikis because of these duplicates.
On GitLab.com, there are 56 rows with duplicate entries by project_id, and 16,661 rows with NULL project_id values.

We use this to filter runner and will use this increasingly in future
instead of is_shared so it should be indexed

# Conflicts:
#   db/schema.rb

Add missing pipeline build foreign key to the schema

See merge request gitlab-org/gitlab-ce!18846

Add tmp index to ci_builds to optimize stages migration

Closes #46179

See merge request gitlab-org/gitlab-ce!18844

Set `ci_runners.runner_type` not null

See merge request gitlab-org/gitlab-ce!18825

15fcd9650f6a4a5832e2ed57419b11e30d3f606f (!18547) squashes old migrations
to a single one.

Old migrations had `rubocop:disable all` rule, but the new migration doesn't
have it, so the `downtime_check` fails.

This commit explicitly tells that the migration requires downtime.