This backports to CE changes that allow the recording of the
repository_type in the table lfs_objects_projects.

This is in order to allow future pruning of unreferenced LFS objects,
as we will need to know which repository to look in for the LFS pointer
file.

The EE MR that contains the original code and a full explanation of the
changes is
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/13894

EE Issue https://gitlab.com/gitlab-org/gitlab-ee/issues/9490

Note that there was a lot of CE code changed in the EE MR because we
want to allow the wiki repository to also use LFS. See
https://gitlab.com/gitlab-org/gitlab-ce/issues/43721. As the wiki is
an unlicensed feature, a full backport is required to enable this.

Adds `# frozen_string_literal: true` to spec/models ruby files

Add an index to the `file_store` column on `lfs_objects`. This makes
counting local objects faster.

Also, there is no longer need to check for objects with `file_store`
being `NULL`. See
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18557

---

### Query plans

#### Before & with `NULL`

```
Aggregate  (cost=113495.96..113495.97 rows=1 width=8) (actual time=1691.394..1691.394 rows=1 loops=1)
  ->  Seq Scan on lfs_objects  (cost=0.00..106415.50 rows=2832186 width=0) (actual time=0.012..1312.488 rows=2852607 loops=1)
        Filter: ((file_store = 1) OR (file_store IS NULL))
        Rows Removed by Filter: 131
Planning time: 0.077 ms
Execution time: 1691.433 ms
```

#### Before, without `NULL`

```
Aggregate  (cost=113495.96..113495.97 rows=1 width=8) (actual time=856.423..856.424 rows=1 loops=1)
  ->  Seq Scan on lfs_objects  (cost=0.00..106415.50 rows=2832186 width=0) (actual time=0.012..672.181 rows=2852607 loops=1)
        Filter: (file_store = 1)
        Rows Removed by Filter: 131
Planning time: 0.128 ms
Execution time: 856.470 ms
```

#### After & with `NULL`

```
Aggregate  (cost=68819.95..68819.96 rows=1 width=8) (actual time=583.355..583.355 rows=1 loops=1)
  ->  Index Only Scan using index_lfs_objects_on_file_store on lfs_objects  (cost=0.43..61688.35 rows=2852643 width=0) (actual time=0.028..399.177 rows=2852607 loops=1)
        Filter: ((file_store = 1) OR (file_store IS NULL))
        Rows Removed by Filter: 131
        Heap Fetches: 867
Planning time: 0.096 ms
Execution time: 583.404 ms
```

#### After, without `NULL`

```
Aggregate  (cost=68817.29..68817.30 rows=1 width=8) (actual time=490.550..490.551 rows=1 loops=1)
  ->  Index Only Scan using index_lfs_objects_on_file_store on lfs_objects  (cost=0.43..61685.68 rows=2852643 width=0) (actual time=0.040..311.760 rows=2852607 loops=1)
        Index Cond: (file_store = 1)
        Heap Fetches: 831
Planning time: 0.294 ms
Execution time: 490.590 ms
```

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/6067

Old records have a null value of file_store column.
This causes the problems with current direct_upload implementation,
as this makes it to choose Store::REMOTE instead of Store::LOCAL.

This change moves the store save when change saving the object.

Fix migrate! method (Minimal fix with ExclusiveLock to prevent race conditions)

Closes #4928 and #4980

See merge request gitlab-org/gitlab-ee!4624

Fix migrate! method (Minimal fix with ExclusiveLock to prevent race conditions)

Closes #4928 and #4980

See merge request gitlab-org/gitlab-ee!4624

Move uploads to object storage

Closes #4163

See merge request gitlab-org/gitlab-ee!3867

Transfer job archives after creation

See merge request gitlab-org/gitlab-ee!3646