Issue 3284 bfloat

[BrianLii]

Why?

We want to use bfloat16 (BF16) in FDL to reduce payload size while keeping a wide exponent range (common in ML/AI workflows). Fory currently lacks a BF16 primitive and optimized arrays. This PR adds full support for bfloat16 in the Fory Go runtime and codegen.

What does this PR do?

1. Compiler:
   • Adds bfloat16 to the IR type system (PrimitiveKind).
   • Updates the Go generator to map bfloat16 to bfloat16.BFloat16 and handle imports.
   • Adds codegen tests for bfloat16.
2. Go Runtime:
   • Adds a new package go/fory/bfloat16 with a strong type type BFloat16 uint16.
   • Implements IEEE 754 compliant conversions between float32 and bfloat16 (round-to-nearest, ties-to-even).
   • Handles special values: NaN, Inf, ±0 correctly.
3. Serialization:
   • Implements optimized serializers for bfloat16, []bfloat16, and [N]bfloat16, mirroring the float16 implementation structure.
4. Type System:
   • Updates TypeResolver to register BFloat16, []BFloat16, and [N]BFloat16 types.
   • Adds type resolution logic to distinguish BFloat16 from uint16 (since it's an alias type) for correct serializer selection.
5. Tests: Adds comprehensive unit tests for conversions, rounding logic, serialization, and codegen.

Related issues

Fixes #3284

Does this PR introduce any user-facing change?

• Does this PR introduce any public API change?
• Does this PR introduce any binary protocol compatibility change?

Benchmark

[chaokunyang]

Please read https://github.com/apache/fory/blob/main/CONTRIBUTING.md#how-to-title-your-pr to update PR title

[BrianLii]

Please read https://github.com/apache/fory/blob/main/CONTRIBUTING.md#how-to-title-your-pr to update PR title

Thank you very much for the reference. I tried to update the title, but I did not see the edit option.

The edit option looks like this:

reference: This GitHub official tutorial