nim-bindings: Fix GCC-14 [-Wincompatible-pointer-types] issue

[jangko]

GCC-14 no longer automatically convert between pointer values of unrelated pointer types.

[asn-d6]

Hey @jangko . Thanks for the PR!

I'm leaning towards ACKing it, but since it involves some low-level nim decisions, would it be possible to get another person of your team (i.e. another nim expert) to review your PR?

[jangko]

ping @tersec @arnetheduck @cheatfate

[jangko]

After discussion with other nimbus developers, we decide to take one step further by introducing breaking changes. Instead of Nim-array to C-struct conversion using pointer casting, we choose to use the C types directly in both kzg.nim and kzg_ex.nim and avoid aliasing rules violation altogether.

Further review and approval will come after we solve issues in other wrapper libraries to make sure no more surprises from gcc-14.

[jtraglia]

LGTM 👍 I don't see any obvious problems.