fix unsafe uintptr usage to be GC-safe on go1.25

Replace uintptr fields with typed pointers so the GC considers them alive.

relates to changes in go1.25: https://go.dev/doc/go1.25#faster-slices

> Faster slices
>
> The compiler can now allocate the backing store for slices on the stack
> in more situations, which improves performance. This change has the potential
> to amplify the effects of incorrect `unsafe.Pointer` usage, see for example
> [issue 73199]. In order to track down these problems, the [bisect tool] can
> be used to find the allocation causing trouble using the `-compile=variablemake`
> flag. All such new stack allocations can also be turned off using
> `-gcflags=all=-d=variablemakehash=n`.

[issue 73199]: https://go.dev/issue/73199
[bisect tool]: https://pkg.go.dev/golang.org/x/tools/cmd/bisect

Assisted-by: OpenAI ChatGPT
Signed-off-by: Sebastiaan van Stijn <[email protected]>

Author: thaJeztah