core/core_timing: Make callback parameters consistent

In some cases, our callbacks were using s64 as a parameter, and in other
cases, they were using an int, which is inconsistent.

To make all callbacks consistent, we can just use an s64 as the type for
late cycles, given it gets rid of the need to cast internally.

While we're at it, also resolve some signed/unsigned conversions that
were occurring related to the callback registration.

src/core/hle/kernel/kernel.cpp

@@ -29,7 +29,7 @@ namespace Kernel {
  * @param thread_handle The handle of the thread that's been awoken
  * @param cycles_late The number of CPU cycles that have passed since the desired wakeup time
  */
-static void ThreadWakeupCallback(u64 thread_handle, [[maybe_unused]] int cycles_late) {
+static void ThreadWakeupCallback(u64 thread_handle, [[maybe_unused]] s64 cycles_late) {
     const auto proper_handle = static_cast<Handle>(thread_handle);
     const auto& system = Core::System::GetInstance();