Impl sceSystemServiceLoadExec (#3647)

* Add support for restarting the emulator with new configurations

- Implement `Restart` function in `Emulator` to enable process relaunch with updated parameters.
- Modify `sceSystemServiceLoadExec` to use the restart functionality.

* Add logging for emulator restart and system service load execution

* Add IPC emulator PID output command

Impl `PID` output command to return the emulator process ID
- required for launches supporting emulator restart

* Add log file append mode support (used after restarting to keep the same log file)

* Keep game root between restarts

* add --wait-for-debugger option flag

* add --wait-for-pid flag

used for sync between parent & child process during restart

* impl restart via ipc

* fix override game root

* add qt flags to allow restart

src/common/logging/backend.cpp

@@ -61,8 +61,9 @@ private:
  */
 class FileBackend {
 public:
-    explicit FileBackend(const std::filesystem::path& filename)
-        : file{filename, FS::FileAccessMode::Write, FS::FileType::TextFile} {}
+    explicit FileBackend(const std::filesystem::path& filename, bool should_append = false)
+        : file{filename, should_append ? FS::FileAccessMode::Append : FS::FileAccessMode::Write,
+               FS::FileType::TextFile} {}
 
     ~FileBackend() = default;
 
@@ -145,6 +146,11 @@ public:
         initialization_in_progress_suppress_logging = false;
     }
 
+    static void ResetInstance() {
+        initialization_in_progress_suppress_logging = true;
+        instance.reset();
+    }
+
     static bool IsActive() {
         return instance != nullptr;
     }
@@ -157,6 +163,10 @@ public:
         instance->StopBackendThread();
     }
 
+    static void SetAppend() {
+        should_append = true;
+    }
+
     Impl(const Impl&) = delete;
     Impl& operator=(const Impl&) = delete;
 
@@ -218,7 +228,7 @@ public:
 
 private:
     Impl(const std::filesystem::path& file_backend_filename, const Filter& filter_)
-        : filter{filter_}, file_backend{file_backend_filename} {}
+        : filter{filter_}, file_backend{file_backend_filename, should_append} {}
 
     ~Impl() = default;
 
@@ -264,6 +274,7 @@ private:
     }
 
     static inline std::unique_ptr<Impl, decltype(&Deleter)> instance{nullptr, Deleter};
+    static inline bool should_append{false};
 
     Filter filter;
     DebuggerBackend debugger_backend{};
@@ -292,6 +303,11 @@ void Stop() {
     Impl::Stop();
 }
 
+void Denitializer() {
+    Impl::Stop();
+    Impl::ResetInstance();
+}
+
 void SetGlobalFilter(const Filter& filter) {
     Impl::Instance().SetGlobalFilter(filter);
 }
@@ -300,6 +316,10 @@ void SetColorConsoleBackendEnabled(bool enabled) {
     Impl::Instance().SetColorConsoleBackendEnabled(enabled);
 }
 
+void SetAppend() {
+    Impl::SetAppend();
+}
+
 void FmtLogMessageImpl(Class log_class, Level log_level, const char* filename,
                        unsigned int line_num, const char* function, const char* format,
                        const fmt::format_args& args) {