[composite compliance testing] Refactor check_backward_formula to accept Callable (#81059)
Maybe niche, but for one-off debugging purposes, I want a variant of
check_backward_formula that accepts a callable rather than an OpInfo.
This is because when debugging, I try to create a repro that does not
involve OpInfos because OpInfos are difficult to deal with (they have
a lot of sample inputs, I may want to test my own sample inputs without
creating a new OpInfo, etc).
This PR refactors check_backward_formula so that it accepts a Callable
instead of an OpInfo. Example usage:
```
import torch
from torch.testing._internal.composite_compliance import check_backward_formula
x = torch.tensor([[1., 1.], [1., 0.]], requires_grad=True)
args = (x, 1)
check_backward_formula_callable(torch.prod, args, {})
```
Test Plan:
- run existing tests
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81059
Approved by: https://github.com/kshitij12345, https://github.com/ezyang
