parse logic will only run if the executable accept args.
healthcheck is the only one not accepting arguments.

- We start supporting the "color" format for logs.
- We now respond to SIGHUP by reopening the log file.
- We now respect the log format when no log filename is specified.

Output to syslog in the event of logging system setup is preserved in
OpenSSH mode.

Changelog: added

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

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

This restores the previous behavior of logging the success and failures
of internal HTTP requests.

Part of https://gitlab.com/gitlab-org/gitlab/issues/207916