[code-reflection] RFR: [hat] varStoreOp extended for dialect varOp Types

[Juan Fumero]

This PR extends the C99 codegen to generate stores for the `VarStoreOp` that corresponds to custom stores for the HAT Dialect. 

For example:


acc = PrivateDataStructure.createPrivate();
...
acc = F16.add(acc, mul);


This patch has been tested for both the OpenCL and CUDA backends.

-------------

Commit messages:
 - [hat] varStoreOp extended for dialect varOp Types

Changes: https://git.openjdk.org/babylon/pull/709/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=709&range=00
  Stats: 34 lines in 8 files changed: 9 ins; 2 del; 23 mod
  Patch: https://git.openjdk.org/babylon/pull/709.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/709/head:pull/709

PR: https://git.openjdk.org/babylon/pull/709