Remove LazyStreamContext (2 out of 2) (#59299)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59299
After recent changes, LazyStreamContext had in fact always become eager, and was in fact equivalent to a vector of streams. So it makes more sense now to remove this abstraction and use a more self-descriptive type.
This PR migrates the TensorPipe agent. The previous PR migrated the RequestCallback internals.
ghstack-source-id: 130583773
Test Plan: CI
Reviewed By: mrshenli
Differential Revision: D28789174
fbshipit-source-id: a27d2b1f40ab3cf2ac0dd946232fd0eecda6d450
