Rename capacity to nbytes in ShareExternalPointer to avoid confusion in future (#41461)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41461
capacity is misleading, and we have many wrong uses internally. Let's rename to nbytes to avoid the confusion in future. Ultimately, we could remove this parameter if possible.
So far I haven't seen any case this capacity is necessary.
Test Plan: oss ci
Differential Revision: D22544189
fbshipit-source-id: f310627f2ab8f4ebb294e0dd5eabc380926991eb
