OpInfo: Extend natural syntax to allow adding metadata (#85890)
Splitting into a seperate PR in case of bike shedding. We can't use
the normal fluent syntax `SampleInput(x).name("foo")` because `.name`
is already how the metadata is accessed. So instead, this adds a
single function where you pass keyword arguments to fill in the
metadata, e.g.
```
SampleInput(x).with_metadata(
name="foo", output_process_fn_grad=out_fn)
```
An alternative closer to the normal fluent style would be to adding a
prefix to the property's name, e.g.
```
(SampleInput(x)
.with_name("foo")
.with_output_process_fn_grad(out_fn))
```
However, I have a slight preference for the `with_metadata` style
because you don't need to add extra parenthesis to break lines.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85890
Approved by: https://github.com/mruberry
