[code-reflection] RFR: [hat] Proposal for bfloat16 [v2]

[Juan Fumero]

> This PR introduces the type [`bfloat16`](https://cloud.google.com/blog/products/ai-machine-learning/bfloat16-the-secret-to-high-performance-on-cloud-tpus) for HAT.
> 
> Testing for OpenCL:
> 
> 
> HAT=SHOW_CODE java -cp hat/job.jar hat.java test ffi-opencl hat.test.TestBFloat16Type
> 
> 
> Testing for CUDA:
> 
> 
> HAT=SHOW_CODE java -cp hat/job.jar hat.java test ffi-cuda hat.test.TestBFloat16Type
> 
> 
> Some tests are expecting to fail due to precision error. We will need to improve the type conversion with round-to-nearest-even for example.

Juan Fumero has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 22 commits:

 - [hat] abstracting the OpenCL and CUDA code builders
 - Merge branch 'code-reflection' into hat/type/bfloat16
 - Merge branch 'code-reflection' into hat/type/bfloat16
 - [hat] remove custom Op for bfloat
 - single line imports in hat code builders
 - single line imports in hat code builders
 - [hat] test matmul with bfloat16
 - [hat] dialect for bfloat16 removed
 - [hat] new test file included in the hat test list
 - [hat] OpenCL handler for bfloat16 via float convs
 - ... and 12 more: https://git.openjdk.org/babylon/compare/0a7929cc...ddc932c3

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Changes: https://git.openjdk.org/babylon/pull/716/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=716&range=01
  Stats: 1620 lines in 28 files changed: 1463 ins; 76 del; 81 mod
  Patch: https://git.openjdk.org/babylon/pull/716.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/716/head:pull/716

PR: https://git.openjdk.org/babylon/pull/716