[code-reflection] RFR: [hat] Remove device custom data types that inherit from Buffer

[Juan Fumero]

This PR removes the codegen that implemented the logic for processing custom data types for device types that inherit from the iFace buffer. 

>From now on,  iFace buffers represent data represent  to be allocated and pass to device's global memory. 
These buffers backup memory segment on the CPU. 

For device types, we can build custom data types as well but they inherit from `DeviceType`. For example, local memory, and private memory. 

How to test:


java @hat/test-suite ffi-opencl 

java @hat/test-suite ffi-cuda

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Commit messages:
 - minor chanage - formatter
 - [hat] obtain varOp name for the CUDA Vector BinOps
 - [hat] DeviceType via iFace buffers removed

Changes: https://git.openjdk.org/babylon/pull/751/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=751&range=00
  Stats: 118 lines in 4 files changed: 30 ins; 57 del; 31 mod
  Patch: https://git.openjdk.org/babylon/pull/751.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/751/head:pull/751

PR: https://git.openjdk.org/babylon/pull/751