[WebNN] Allow ops to handle ignoring an empty tensor as input (#22972)
### Description
Some ops should allow empty tensor as input, e.g. roi, scales inputs in
Resize
### Motivation and Context
It avoid some unexpected fallback for optional input with empty tensor.
e.g. roi and scales are both optional inputs in Resize, in some models
they have non-empty name but with empty initializer presented as `[0]`,
WebNN currently will fallback all nodes with 0 dimension, which is not
expected.
