Backport of qemu: reduce monitor socket path into release/1.3.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #13971 to be assessed for backporting due to the inclusion of the label backport/1.3.x.

The below text is copied from the body of the original PR.

---

The QEMU driver can take an optional graceful_shutdown configuration
which will create a Unix socket to send ACPI shutdown signal to the VM.

Unix sockets have a hard length limit and the driver implementation
assumed that QEMU versions 2.10.1 were able to handle longer paths. This
is not correct, the linked QEMU fix only changed the behaviour from
silently truncating longer socket paths to throwing an error.

By validating the socket path before starting the QEMU machine we can
provide users a more actionable and meaningful error message, and by
using a shorter socket file name we leave a bit more room for
user-defined values in the path, such as the task name.

The maximum length allowed is also platform-dependant, so validation
needs to be different for each OS.

[github-actions]

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.