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/core/hardware_properties.h

@@ -9,12 +9,13 @@
 
 #include "common/bit_util.h"
 #include "common/common_types.h"
+#include "common/settings.h"
 
 namespace Core {
 
 namespace Hardware {
 
-constexpr u64 BASE_CLOCK_RATE = 1'020'000'000; // Default CPU Frequency = 1020 MHz
+inline u64 BASE_CLOCK_RATE() { return Settings::values.cpu_clock_rate.GetValue(); } // Default CPU Frequency set in settings, defaults to 1020 MHz
 constexpr u64 CNTFREQ = 19'200'000;            // CNTPCT_EL0 Frequency = 19.2 MHz
 constexpr u32 NUM_CPU_CORES = 4;               // Number of CPU Cores
 

src/core/hle/service/apm/apm_controller.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2019 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <algorithm>
@@ -81,8 +82,8 @@ PerformanceConfiguration Controller::GetCurrentPerformanceConfiguration(Performa
 
 void Controller::SetClockSpeed(u32 mhz) {
     LOG_DEBUG(Service_APM, "called, mhz={:08X}", mhz);
-    // TODO(DarkLordZach): Actually signal core_timing to change clock speed.
-    // TODO(Rodrigo): Remove [[maybe_unused]] when core_timing is used.
+    // Update the clock rate setting with the provided MHz value (convert to Hz)
+    Settings::values.cpu_clock_rate = mhz * 1'000'000;
 }
 
 } // namespace Service::APM