Support implicit array conversion with query-planning enabled

[rjzamora]

Description

when query-planning is enabled, implicit conversion is not yet supported from a cudf-backed collection to a dask array. Some cuml + dask CI failures are related to this limitation. This PR adds basic support for implicit conversion.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[wence-]

Makes sense. I suppose there's no need to push upstream because the intent is for this code (afaict from https://github.com/dask/dask-expr/blob/2f5f085511986e51d75caa499e3eab67a8c8b186/dask_expr/_backends.py#L80) to not be long-lived?

[rjzamora]

Makes sense. I suppose there's no need to push upstream because the intent is for this code (afaict from https://github.com/dask/dask-expr/blob/2f5f085511986e51d75caa499e3eab67a8c8b186/dask_expr/_backends.py#L80) to not be long-lived?

Yeah, I'm hoping that the long-term fix for create_array_collection will be able to leverage the dispatch logic that is already upstream.

[rjzamora]

/merge