Move cuda/runtime/shim to cuda/runtime for better usibility.

[Gasoonjia]

Stack from ghstack (oldest at bottom):

• (to be filled)

This diff moves the cuda/runtime/shim directory to cuda/runtime to make the utility functions sharable among all runtime infrastructure.

Differential Revision: D84122729

[pytorch-bot]

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❌ 1 New Failure

As of commit 3d62bd4 with merge base e09abea ():

NEW FAILURE - The following job has failed:

• Propose to merge ghstack orig PRs to main / Try to create a PR with ghstack /orig branch (gh)
  Process completed with exit code 1.

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