general: Get the current process program id directly from the system

This allows us to avoid including KProcess' header file in files that only need to get the current process' program id.

src/yuzu/bootmanager.cpp

@@ -32,7 +32,6 @@
 #include "common/settings.h"
 #include "core/core.h"
 #include "core/frontend/framebuffer_layout.h"
-#include "core/hle/kernel/k_process.h"
 #include "input_common/keyboard.h"
 #include "input_common/main.h"
 #include "input_common/mouse/mouse_input.h"
@@ -66,7 +65,7 @@ void EmuThread::run() {
 
     if (Settings::values.use_disk_shader_cache.GetValue()) {
         system.Renderer().ReadRasterizer()->LoadDiskResources(
-            system.CurrentProcess()->GetProgramID(), stop_token,
+            system.GetCurrentProcessProgramID(), stop_token,
             [this](VideoCore::LoadCallbackStage stage, std::size_t value, std::size_t total) {
                 emit LoadProgress(stage, value, total);
             });