Bump width of `AttributeBitSet` to 16 bytes

[yuxuanchen1997]

With my recent rebase of #99282, I discovered that my code no longer compiles because we have more than 96 attributes. There's a static assertion that prevents the current AttributeBitSet from overflowing and the current width for the bitset is 12 bytes.

https://github.com/llvm/llvm-project/blob/main/llvm/lib/IR/AttributeImpl.h#L278

I propose that we should for now bump the width to 16 bytes (128 unique attributes).

[yuxuanchen1997]

@nikic, you originally added the class and just let me know if you are ok with it.

[nikic]

Bumping to 16 bytes is fine.

[yuxuanchen1997]

#106138