Puma has a limit (`Puma::Const::MAX_BODY` - around 110 KiB) over which
it will write request bodies to disk for handing off to the
application. When it does this, the request body can be left on disk
if the Puma process receives SIGKILL. Consider an extremely minimal
`config.ru`:

    run(proc { [204, {}, []] })

If we then:

1. Start `puma`, noting the process ID.
2. Start a slow file transfer, using `curl --limit-rate 100k` (for
   example) and `-T $PATH_TO_LARGE_FILE`.
3. Watch `$TMPDIR/puma*`.

We will see Puma start to write this temporary file. If we then send
SIGKILL to Puma, the file won't be cleaned up. With this patch, it
will.

The patch itself is pretty unpleasant: as Puma has two quite long
methods that set up the temporary files (`Puma::Client#setup_body` and
`Puma::Client#setup_chunked_body`), we have to copy those methods and
call `#unlink` in the correct spots in both. Also, as these are private
methods, it's hard to write a test for them. We can test manually.
Running `fswatch -t -x $TMPDIR | grep puma` while posting a large file
shows this with this patch:

    Fri Mar 26 20:34:10 2021 ... Created Removed IsFile
    Fri Mar 26 20:34:21 2021 ... Updated IsFile

Whereas without this patch we get:

    Fri Mar 26 20:32:57 2021 ... Created IsFile
    Fri Mar 26 20:33:05 2021 ... Created Removed Updated IsFile

Rack writes files from multipart/form-data requests to disk in a
temporary file. Rack includes a middleware to clean these up -
Rack::TempfileReaper - but that won't withstand a process being sent
SIGKILL. To handle that case, we can immediately unlink the created
temporary file, which means it will be removed once we're done with it
or the current process goes away.

For development mode and test mode, we have to ensure that this new
middleware is before Gitlab::Middleware::Static, otherwise we might not
get the chance to set our own middleware.

With direct upload configured, GitLab mostly doesn't accept
multipart/form-data requests in a way where they reach Rack directly -
they typically go via Workhorse which accelerates them - but there are
cases where it can happen, and direct upload is still only an option.

To test this manually, we can set `$GITLAB_API_TOKEN_LOCAL` to a
personal access token for the API in the local environment,
`$PATH_TO_FILE` to be a path to a (preferably large) file to be
uploaded, and break the actual saving of uploads (in the default case
with GDK, stop Minio):

    curl -H "Private-Token: $GITLAB_API_TOKEN_LOCAL" \
      -F "file=@$PATH_TO_FILE" \
      http://localhost:3000/api/v4/projects/1/uploads

Once the upload is finished and the request fails, we'll see the file we
uploaded in `$TMPDIR`:

    $ ls -l $TMPDIR/RackMultipart* | awk '{ print $5, $8 }'
    952107008 17:40

With this change, that won't happen: we'll see the file created and
immediately unlinked, so no matter what happens, it won't stick around
on disk. (This specific test case is handled by Rack::TempfileReaper in
later versions of Rack, but it still depends on manual cleanup.)

Merge branch '325263-wiki-kerberos-clone-button-fails-with-undefined-local-variable-or-method-project' into 'master'

Fix 500 error when cloning a wiki using the Kerberos clone button

See merge request gitlab-org/gitlab!58270

Fix EmptyLineAfterFinalLetItBe offenses in spec/services/groups

See merge request gitlab-org/gitlab!58423

Migrate delete label modal to Vue

See merge request gitlab-org/gitlab!58131

Update default branch in divergence graph

See merge request gitlab-org/gitlab!58871

Change to "read-write" rather than "read write" in database_spec.rb

See merge request gitlab-org/gitlab!59067

Merge branch '247515-the-ssh-key-page-at-profile-keys-should-mention-that-expired-keys-only-cause-warnings-and' into 'master'

The SSH Key page should mention that expired keys only cause warnings and will continue working

See merge request gitlab-org/gitlab!57494

Fix EmptyLineAfterFinalLetItBe offenses in spec/services/issues

See merge request gitlab-org/gitlab!58425

Geo: Add logging to help diagnose why syncing is not working

See merge request gitlab-org/gitlab!58526

Ensure project_iid before calling drop! on the pipeline [RUN ALL RSPEC] [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!57783

Add new project sidebar panel

See merge request gitlab-org/gitlab!58854

Make blobs directly accessible through the graphql repository

See merge request gitlab-org/gitlab!58677

Expose timelogs against issues and merge requests in graphql

See merge request gitlab-org/gitlab!57321

Remove mock data from DAST Site Profiles

See merge request gitlab-org/gitlab!58735

Fix RSpec/EmptyLineAfterFinalLetItBe for ee/spec/services/merge_trains

See merge request gitlab-org/gitlab!58333

Fix EmptyLineAfterFinalLetItBe offenses in spec/lib/gitlab/hook_data

See merge request gitlab-org/gitlab!58262

Fix N+1 queries to find or initialize services

See merge request gitlab-org/gitlab!58879

Fix EmptyLineAfterFinalLetItBe offenses in spec/services/ide

See merge request gitlab-org/gitlab!58424

Fix timeout error when loading pipelines by commit SHA for GraphQL

See merge request gitlab-org/gitlab!59110

Use object quarantine directory to enumerate new LFS pointers [RUN ALL RSPEC] [RUN AS-IF-FOSS]

See merge request gitlab-org/gitlab!58634

Fix EmptyLineAfterFinalLetItBe offenses in spec/services/merge_requests

See merge request gitlab-org/gitlab!58429

Include context in spec time tracking

See merge request gitlab-org/gitlab!58980

Fix cop offenses for Style/HashTransformation in spec directory

See merge request gitlab-org/gitlab!56586

Fix cop offenses for Style/HashTransformation in ee directory

See merge request gitlab-org/gitlab!56581

Add Billable Memberships API

See merge request gitlab-org/gitlab!58506

Set version when externally installed

See merge request gitlab-org/gitlab!58852

It was loading all the pipelines for a given project and tried to match
them from with the requested one from Ruby. This was causing database
statement timeouts for projects with lots of pipelines.

Fix RSpec/EmptyLineAfterFinalLetItBe for ee/spec/features/admin

See merge request gitlab-org/gitlab!58403