[code-reflection] Integrated: Moved PTX backend functionality to CUDA backend

[Gary Frost]

Moved the required PTX generation code into the more general CUDA backend.

We can select PTX generation either by sending a config string including 'PTX' to the backend (default will be Cuda C99)

We can also add PTX to HAT env var at launch


HAT=INFO,PTX java @hat/run ffi-cuda squares

vs

HAT=INFO java @hat/run ffi-cude squares

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Commit messages:
 - Moved PTX backend functionality to CUDA backend

Changes: https://git.openjdk.org/babylon/pull/384/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=384&range=00
  Stats: 1609 lines in 14 files changed: 1507 ins; 49 del; 53 mod
  Patch: https://git.openjdk.org/babylon/pull/384.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/384/head:pull/384

PR: https://git.openjdk.org/babylon/pull/384