[JIT] additional support for CallMethod with autocasting (#67925)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67925
Previously, the following would always fail, because autocasting would not be enabled in the called method:
```
torch.jit.script
def fn(x, y):
with autocast():
# CallMethod() to some method
fn(x, y)
```
This allows the above, if autocasting is globally enabled, e.g.
```
torch.jit.script
def fn(x, y):
with autocast():
# CallMethod() to some method
with autocast():
fn(x, y) # now
```
ghstack-source-id: 142667351
Test Plan: added test in test_jit_autocast.py
Reviewed By: navahgar
Differential Revision: D32214439
fbshipit-source-id: bb7db054e25e18f5e3d2fdb449c35b5942ab303e
