feat: add CPU clock rate slider to settings

Implement a slider in the CPU settings tab to adjust the BASE_CLOCK_RATE
up to 1,785 MHz (Switch's official maximum clock rate). Default remains
at 1,020 MHz.

This change:
- Adds UI slider and spinbox to configure_cpu.ui with range 500-1785 MHz
- Makes BASE_CLOCK_RATE dynamic by reading from settings
- Modifies WallClock to handle dynamic clock rate changes
- Updates APM controller to properly set the clock rate
- Changes clock rate settings category from Core to CPU

The user can now easily adjust the CPU clock rate to improve performance
or manage thermals and power consumption.

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/common/settings.h

@@ -199,6 +199,7 @@ struct Values {
                                                              MemoryLayout::Memory_12Gb,
                                                              "memory_layout_mode",
                                                              Category::Core};
+    SwitchableSetting<u32> cpu_clock_rate{linkage, 1'020'000'000, "cpu_clock_rate", Category::Cpu};
     SwitchableSetting<bool> use_speed_limit{
         linkage, true, "use_speed_limit", Category::Core, Specialization::Paired, false, true};
     SwitchableSetting<u16, true> speed_limit{linkage,