Update cross-curve-dleq dependency

Making build times considerably faster.

On my machine, after running `cargo clean`, `cargo build -p swap`
takes 2min 19s.

The updated dependency also comes with a critical fix to the `Scalar`
type, which originally wrongly assumed that secp256k1 and ed25519
scalars had the same endianness. For this reason, we now have to
reverse the bytes of recovered scalars if we are to use them on a
different chain.

Finally, there is no need to append `RUST_MIN_STACK=100000000` to
avoid stack overflows in tests and when running the binary.

xmr-btc/tests/e2e.rs

@@ -1,11 +1,6 @@
 pub mod harness;
 
 mod tests {
-    // NOTE: For some reason running these tests overflows the stack. In order to
-    // mitigate this run them with:
-    //
-    //     RUST_MIN_STACK=100000000 cargo test
-
     use crate::{
         harness,
         harness::{