[code-reflection] Integrated: Removed ptx backend

[Gary Frost]

The previous PR moved ptx backend functionality to Cuda backend.  So just removing the redundant files and project artifacts

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Commit messages:
 - Removed ptx backend

Changes: https://git.openjdk.org/babylon/pull/385/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=385&range=00
  Stats: 2467 lines in 15 files changed: 0 ins; 2467 del; 0 mod
  Patch: https://git.openjdk.org/babylon/pull/385.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/385/head:pull/385

PR: https://git.openjdk.org/babylon/pull/385