[mlir][Target] Teach dense_resource conversion to LLVMIR Target (#78958)

This patch adds support for translating dense_resource attributes to
LLVMIR Target.
The support added is similar to how DenseElementsAttr is handled, except
we
don't need to handle splats.

Another possible way of doing this is adding iteration on
dense_resource, but that is
non-trivial as DenseResourceAttr is not meant to be something you should
directly
access. It has subclasses which you are supposed to use to iterate on
it.