Use SizedUnsignedType_t to pick UnsignedType for uniform_integer_distribution

The previously used `make_unsigned` approach combined with the overload
set of `extendedMult` caused compilation issues on MacOS platform. By
forcing the selection to be one of `std::uintX_t` types we don't need
to complicate the overload set further.

tests/SelfTest/IntrospectiveTests/RandomNumberGeneration.tests.cpp

@@ -140,7 +140,9 @@ TEMPLATE_TEST_CASE( "uniform_integer_distribution can handle unit ranges",
                     uint32_t,
                     int32_t,
                     uint64_t,
-                    int64_t ) {
+                    int64_t,
+                    size_t,
+                    ptrdiff_t) {
     // We want random seed to sample different parts of the rng state,
     // the output is predetermined anyway
     std::random_device rd;