PR #13568: [GPU] Let constants be emitted into a separate LLVM module.
PR #13568: [GPU] Let constants be emitted into a separate LLVM module.

Imported from GitHub PR https://github.com/openxla/xla/pull/13568

Will not change the behavior of the compiler for now - the use of separate constant modules will be added in the next PR with on-disk kernel compilation cache: https://github.com/openxla/xla/pull/13569.
Copybara import of the project:

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6c366cf77a749f10c9e23a52e4ee7b16359baaf8 by Ilia Sergachev <isergachev@nvidia.com>:

[GPU] Let constants be emitted into a separate LLVM module.

Merging this change closes #13568

FUTURE_COPYBARA_INTEGRATE_REVIEW=https://github.com/openxla/xla/pull/13568 from openxla:consts_module 6c366cf77a749f10c9e23a52e4ee7b16359baaf8
