PR #11353: Implement async dynamic slicing
PR #11353: Implement async dynamic slicing

Imported from GitHub PR https://github.com/openxla/xla/pull/11353

This implements async dynamic-slice and dynamic-update-slice for host memory offloading on GPU.

Since the emitter does not understand dynamic slicing instructions in async computation, we wrap them in a fusion node and mark them for execution on a different stream. This is all we need to execute the offloading of slices asynchronously.
Copybara import of the project:

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905db6df8130300014728bf4eceb2ee2fc23d6e1 by Jaroslav Sevcik <jsevcik@nvidia.com>:

Wrap async dynamic slicing into fusion


Merging this change closes #11353

Reverts changelist 592550538

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/11353 from jaro-sevcik:host-offloading-async-fusion-dynamic-slicing 905db6df8130300014728bf4eceb2ee2fc23d6e1
