In the system scheduler, if a subset of clients are filtered by class,
we hit a code path where the `AllocMetric` has been copied, but the
`Copy` method does not instantiate the various maps. This leads to an
assignment to a nil map. This changeset ensures that the maps are
non-nil before continuing.

The `Copy` method relies on functions in the `helper` package that all
return nil slices or maps when passed zero-length inputs. This
changeset to fix the panic bug intentionally defers updating those
functions because it'll have potential impact on memory usage. See
https://github.com/hashicorp/nomad/issues/11564 for more details.

The QEMU driver allows arbitrary command line options, but many of
these options give access to host resources that operators may not
want to expose such as devices. Add an optional allowlist to the
plugin configuration so that operators can limit the resources for
QEMU.

Update UI dependencies

* debug: refactor Consul API collection
* debug: refactor Vault API collection
* debug: cleanup test timing
* debug: extend test to multiregion
* debug: save cmdline flags in bundle
* debug: add cli version to output
* Add changelog entry