[StaticRuntime] Fix bug in MemoryPlanner (#51342)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51342
There is a subtle bug with the MemoryPlanner with regard to view ops with out variant.
```
def forward(self, a: Tensor, shape: List[int]):
b = a.reshape(shape)
return b + b
```
In this case, if we replace reshape with the out variant, b would be managed by the MemoryPlanner and the storage of its output would have been set to nullptr right after inference by the MemoryPlanner if opts.cleanup_activations is true. Because b is a view of a, the storage of a is also set to nullptr, and this violates the API which promises that a is const.
To fix this bug, I changed the MemoryPlanner so that it puts b in the unmanaged part.
Test Plan:
Add unit test to enforce the constness of inputs
```
buck test //caffe2/benchmarks/static_runtime:static_runtime_cpptest
```
Reviewed By: ajyu
Differential Revision: D26144203
fbshipit-source-id: 2dbacccf7685d0fe0f0b1195166e0510b2069fe3
