LibCrypto: Make the constructors of (Un)SignedBigInteger templated

This means it can take any (un)signed word of size at most Word.
This means the constructor can be disambiguated if we were to add a
double constructor :^).

This requires a change in just one test.

Tests/LibCrypto/TestBigInteger.cpp

@@ -73,7 +73,7 @@ TEST_CASE(test_unsigned_bigint_basic_add_to_accumulator)
 
 TEST_CASE(test_unsigned_bigint_basic_add_to_empty_accumulator)
 {
-    Crypto::UnsignedBigInteger num1({});
+    Crypto::UnsignedBigInteger num1 {};
     Crypto::UnsignedBigInteger num2(10);
     Crypto::UnsignedBigIntegerAlgorithms::add_into_accumulator_without_allocation(num1, num2);
     EXPECT_EQ(num1.words(), Vector<u32> { 10 });

Userland/Libraries/LibCrypto/BigInt/SignedBigInteger.h

@@ -16,9 +16,11 @@ struct SignedDivisionResult;
 
 class SignedBigInteger {
 public:
-    SignedBigInteger(i32 x)
-        : m_sign(x < 0)
-        , m_unsigned_data(abs(x))
+    template<typename T>
+    requires(IsSigned<T> && sizeof(T) <= sizeof(i32))
+        SignedBigInteger(T value)
+        : m_sign(value < 0)
+        , m_unsigned_data(abs(static_cast<i32>(value)))
     {
     }
 

Userland/Libraries/LibCrypto/BigInt/UnsignedBigInteger.h

@@ -24,7 +24,13 @@ public:
     using Word = u32;
     static constexpr size_t BITS_IN_WORD = 32;
 
-    UnsignedBigInteger(Word x) { m_words.append(x); }
+    // This constructor accepts any unsigned with size up to Word.
+    template<typename T>
+    requires(IsIntegral<T> && sizeof(T) <= sizeof(Word))
+        UnsignedBigInteger(T value)
+    {
+        m_words.append(static_cast<Word>(value));
+    }
 
     explicit UnsignedBigInteger(Vector<Word, STARTING_WORD_SIZE>&& words)
         : m_words(move(words))