GHSA-969W-Q74Q-9J8V Unsound API in `secp256k1` allows use-after-free and invalid deallocation from safe code

Because of incorrect bounds on method Secp256k1::preallocatedgennew it was possible to cause use-after-free from safe consumer code. It was also possible to "free" memory not allocated by the appropriate allocator. The method takes a place for storing the context as a mutable reference and return...