[DORT] Enable aten::full by implementing extra logics to select EP (#16699)
DORT only select devices from inputs arguments' (type: torch.Tensor).
However, it errors out when a graph doesn't have any inputs (e.g., a
single aten::full graph). This PR address this problem by changing the
EP selection to
- First, inspect graph inputs. If there are some valid devices, use them
plus a default one (`OrtBackend.ep: str`).
- Otherwise, inspect graph outputs carried by `torch.fx.GraphModule` and
use all valid devices plus the default `OrtBackend.ep`.
- When both (1) and (2) fail, it uses the default EP specified by
`OrtBackend.ep`.