LibCrypto: Add hash methods to {Signed, Unsigned}BigInteger

These just use hash the underlying bytes that make up the integer words

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h

@@ -99,6 +99,8 @@ public:
     SignedBigInteger multiplied_by(const UnsignedBigInteger& other) const;
     SignedDivisionResult divided_by(const UnsignedBigInteger& divisor) const;
 
+    u32 hash() const;
+
     void set_bit_inplace(size_t bit_index);
 
     bool operator==(const SignedBigInteger& other) const;