fix(testing/bench.py): add dict support to _format_value

[pandacooming]

Summary

Add dict handling to _format_value() in tile_kernels/testing/bench.py, formatting dicts as k1=v1,k2=v2 consistent with make_param_key style.

Fixes #6

Changes

def _format_value(value):
    if isinstance(value, torch.dtype):
        return dtype_to_str(value)
    if isinstance(value, tuple):
        return 'x'.join(str(v) for v in value)
+   if isinstance(value, dict):
+       return ','.join(f'{k}={_format_value(v)}' for k, v in sorted(value.items()))
    if value is None:
        return 'None'
    return str(value)

Testing

All cases pass:

{'topk': 2, 'hidden': 256} → hidden=256,topk=2  ✅ (sorted)
{'a': 1, 'b': 2}           → a=1,b=2            ✅
{}                          → (empty string)     ✅
{'outer': {'inner': 1}}    → outer=inner=1      ✅ (recursive)
torch.float16               → fp16               ✅ (still works)
(128, 256)                  → 128x256            ✅ (still works)