Logrus buffers its output internally, which makes these tests fail
intermittently. They're also not a good example to follow generally.

We now have acceptance tests that exercise this functionality so I'm
pretty relaxed about losing the expectations. However, we can test
them by inspecting the server-received metadata too, so there's no loss
of coverage here.

The move from logrus to labkit for logging also makes these tests hard
to justify keeping.

Gitaly project now properly respects module release flow
and includes a module suffix in the package name. It requires
to re-write all non-suffixed imports with suffixed of a specific
version of tha module. With proper module versioning we don't
need to use a 'replace' directive to point to specific commit
and can use semantic versioning for the gitaly dependency.

Part of: https://gitlab.com/gitlab-org/gitaly/-/issues/3177

Previously, opentracing (if configured) was initialized late in the
gitlab-shell process's lifespan, coming just before making a gRPC
call to Gitaly.

By moving the opentracing initialization to be at process startup, we
make it available for the whole process lifecycle, which is very useful
to gitlab-sshd, as it means we'll only call tracing.Initialize() once
on process startup, rather than once per SSH connection.

To get this working, we need to introduce a context to gitlab-sshd.
This carries the client/service name, but also carries an initial
correlation ID. The main outcome of this is that all calls to the
authorized_keys endpoint from a given gitlab-sshd process will now
share a correlation ID. I don't have a strong opinion about this either
way.

Changelog: fixed

Without these changes, Gitaly calls would not be linked to a parent
context. This means that they would have an unassociated correlationID,
and Gitaly RPC calls would not be cancel()ed by parent context
cancellation.

Changelog: fixed

In this case we don't need to propagate cleanup
function. It simplifies the code.

Refactors introspection of execution environment to rely on
per-connection state (`gitlab-shell`) or per request (`gitlab-sshd`)

Relates to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/496

During a SSH receive-pack request (e.g. `git push`), gitlab-shell was
incorrectly using the user returned by the `/internal/allowed` API
endpoint to make an SSHReceivePack RPC call. This caused a number of
problems with deploy keys with write access:

1. Keys that were generated by a blocked user would be denied the
ability to write.

2. Keys that were generated by user that did not have write access to
the project would also be denied.

GitLab 12.4 removed the Ruby implementation of gitlab-shell in favor of
the Golang implementation, and these implementations worked slightly
differently. In
https://gitlab.com/gitlab-org/gitlab-shell/blob/v10.1.0/lib/gitlab_shell.rb,
the Ruby implementation would always use `@who` (e.g. `key-123`), but in
gitlab-shell v10.2.0 the Go implementation would always use the user
from the API response.

Reads did not have this issue because the user/deploy key is never
passed to Gitaly for additional permission checks. Writes need this
information for the pre-receive to check access to protected branches,
push rules, etc.

Relates to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/479

Previously, gitlab-shell did not pass a context through the application.
Correlation IDs were generated down the call stack instead of passed
around from the start execution.

This has several potential downsides:

1. It's easier for programming mistakes to be made in future that lead
to multiple correlation IDs being generated for a single request.
2. Correlation IDs cannot be passed in from upstream requests
3. Other advantages of context passing, such as distributed tracing is
not possible.

This commit changes the behavior:

1. Extract the correlation ID from the environment at the start of
the application.
2. If no correlation ID exists, generate a random one.
3. Pass the correlation ID to the GitLabNet API requests.

This change also enables other clients of GitLabNet (e.g. Gitaly) to
pass along the correlation ID in the internal API requests
(https://gitlab.com/gitlab-org/gitaly/-/issues/2725).

Fixes https://gitlab.com/gitlab-org/gitlab-shell/-/issues/474

This will make it easier to tie an SSH access request to Rails API and
Gitaly requests.