core_timing: Allow configuring a fixed or random initial system tick value. (#7309)

* core_timing: Apply random base ticks value on startup.

* core: Maintain consistent base system ticks in TAS movies.

* frontend: Add setting to configure a fixed base system ticks value.

src/core/movie.h

@@ -74,6 +74,9 @@ public:
     /// Get the init time that would override the one in the settings
     u64 GetOverrideInitTime() const;
 
+    /// Get the base system ticks value that would override the one generated by core timing
+    s64 GetOverrideBaseTicks() const;
+
     struct MovieMetadata {
         u64 program_id;
         std::string author;
@@ -168,7 +171,8 @@ private:
     std::string record_movie_file;
     std::string record_movie_author;
 
-    u64 init_time; // Clock init time override for RNG consistency
+    u64 init_time;       // Clock init time override for RNG consistency
+    s64 base_ticks = -1; // Core timing base system ticks override for RNG consistency
 
     std::vector<u8> recorded_input;
     std::size_t current_byte = 0;