Consolidate `MLD_CONFIG_CUSTOM_ZEROIZE` with mlkem-native

[mkannwischer]

The MLD _CONFIG_CUSTOM_ZEROIZE works slightly different from how MLK_CONFIG_CUSTOM_ZEROIZE works:

mldsa-native/mldsa/src/ct.h

Lines 314 to 320 in 734e659

	#if defined(MLD_CONFIG_CUSTOM_ZEROIZE)
	static MLD_INLINE void mld_zeroize(void *ptr, size_t len)
	{
	mld_zeroize_native(ptr, len);
	}
	#elif defined(MLD_SYS_WINDOWS)
	#include <windows.h>

https://github.com/pq-code-package/mlkem-native/blob/b9bab5b74a612db84ee370ce1cffc5a3948b55e9/mlkem/src/verify.h#L434-L459

We should consolidate that.