feat: add system time offset setting (#6139)

* Add setting for system time offset

Add a setting to displace citra system time by days, hours, minutes
or seconds
Add UI for the setting which is only visible when clock is set to
system time
Change core/settings.h to include the setting

* Add system time offset to kernel

Actually makes use of the time offset.

* Fix time offset calculatioon in core/movie.cpp

* Replace C++20 chrono::days with seconds

Hopefully fixes the build.

src/core/settings.h

@@ -163,6 +163,7 @@ struct Values {
     int region_value;
     InitClock init_clock;
     u64 init_time;
+    s64 init_time_offset;
 
     // Renderer
     bool use_gles;