Partially addresses #47424.

This reverts the addition of the "goldiloader" Gem and all use of it.
While this Gem is very promising it's causing a variety of problems on
GitLab.com due to it eager-loading too much data in places where we
don't expect/can handle this. At least for the time being this means we
have to go back to manually fixing N+1 query problems, but at least
those should not cause a negative impact on availability.

Goldiloader is great, but has several issues with has_many :through relations:

* https://github.com/salsify/goldiloader/issues/12
* https://github.com/salsify/goldiloader/issues/14
* https://github.com/salsify/goldiloader/issues/18

Rather than try to figure out which applies in each case, we should just do the
drudge work of manually disabling autoloading for all relations of this type. We
can always use regular preloading for specific cases, but this way we avoid
generating invalid queries through Goldiloader's magic.

[10.3] Migrate `can_push` column from `keys` to `deploy_keys_project`

See merge request gitlab/gitlabhq!2276

(cherry picked from commit f6ca52d31bac350a23938e0aebf717c767b4710c)

1f2bd3c0 Backport to 10.3

This is allowed for existing instances so we don't end up 76 offenses
right away, but for new code one should _only_ use this if they _have_
to remove non database data. Even then it's usually better to do this in
a service class as this gives you more control over how to remove the
data (e.g. in bulk).

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7383#note_18517263

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7383#note_18439108

- Required on the GitLab Rails side is mostly authentication and API related.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

In 8278b763 the default behaviour of annotation
has changes, which was causing a lot of noise in diffs. We decided in #17382
that it is better to get rid of the whole annotate gem, and instead let people
look at schema.rb for the columns in a table.

Fixes: #17382

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Create DeployKey & DeployKeysProject models. Bulding many to many relation between deploy keys and projects

Users with many projects (>100) will hit the 20 second timeout when
updating the gitolite config. This fix batches those changes into a
signle update to the file, causing an order of magnitude speed increase
which finishes well below the 20 second timeout.

Fixes gitlabhq/gitlabhq#220

  * Remove trailing whitespace
  * Converts hard-tabs into two-space soft-tabs
  * Remove consecutive blank lines