Contributes to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/762

**Problem**

There is a new endpoint for SSH Push implemented in Workhorse. We
want to use it for Geo Git Push calls.

**Solution**

* Define a boolean parameter `GeoProxyPushSSHDirectToPrimary` hidden
behind the feature flag.
* Make a call to `ssh-receive-pack` endpoint for git push commands.

Changelog: added

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/442907

**Problem**

We discovered that reliance on project and namespace paths is not
sufficient. User can rename the group or project and that might lead to
problems with identifying the correct project/namespace.

**Solution**

Instead of project/namespace path we should use their IDs.

Changelog: added

LogData also contains a new LogMetadata struct

Also rename to Metadata

Currently, we perform a request to Gitlab Rails that proxies
the request to primary

However, it causes timeouts on big pushes and consumes large
amount of memory. We can perform an HTTP request directly
from Gitlab Shell instead and stream the response to the user

While gitlab-shell currently has a major version of v14, the module path
it exposes is not using that major version like it is required by the Go
standard. This makes it impossible for dependents to import gitlab-shell
as a dependency without using a commit as version.

Fix this by changing the module path of gitlab-shell to instead be
`gitlab.com/gitlab-org/gitlab-shell/v14` and adjust all imports
accordingly.

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

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

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

We'll reuse this module for uploadpack in the future

Other functions are still expecting for `CommandArgs` instead
of `Shell`. They should be expecting `commandargs.Shell` now
since it has been renamed.