[code-reflection] Integrated: Add CUDA Clion artifacts and cleanup cuda backend

[Gary Frost]

Added CUDA backend cpp files to clion CMakeLists.txt

Cleaned CUDA backend source.

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Commit messages:
 - Add CUDA Clion artifacts and cleanup cuda backend

Changes: https://git.openjdk.org/babylon/pull/85/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=85&range=00
  Stats: 245 lines in 8 files changed: 86 ins; 153 del; 6 mod
  Patch: https://git.openjdk.org/babylon/pull/85.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/85/head:pull/85

PR: https://git.openjdk.org/babylon/pull/85