[code-reflection] Integrated: replaced common ffi-cuda code with ffi-shared

[Gary Frost]

Replaced common code in ffi-cuda backend with common code in ffi-shared.

This finally aligns the codebase for ptx, cuda and opencl. 

Also acts as stable API to refactor HIP and SPIRV backends.

At this time CUDA backend can not minimize buffer copies (JVM crash).  So that will be investigated in the next PR.

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Commit messages:
 - replaced common ffi-cuda code with ffi-shared

Changes: https://git.openjdk.org/babylon/pull/389/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=389&range=00
  Stats: 336 lines in 6 files changed: 121 ins; 157 del; 58 mod
  Patch: https://git.openjdk.org/babylon/pull/389.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/389/head:pull/389

PR: https://git.openjdk.org/babylon/pull/389