[qt] refactor: qt_common lib (#94)

This is part of a series of PRs made in preparation for the QML rewrite. this PR specifically moves a bunch of utility functions from main.cpp into qt_common, with the biggest benefit being that QML can reuse the exact same code through ctx passthrough.

Also, QtCommon::Frontend is an abstraction layer over several previously Widgets-specific stuff like QMessageBox that gets used everywhere. The idea is that once QML is implemented, these functions can have a Quick version implemented for systems that don't work well with Widgets (sun) or for those on Plasma 6+ (reduces memory usage w/o Widgets linkage) although Quick from C++ is actually anal, but whatever.

Other than that this should also just kinda reduce the size of main.cpp which is a 6000-line behemoth rn, and clangd straight up gives up with it for me (likely caused by the massive amount of headers, which this DOES reduce).

In the future, I probably want to create a common strings lookup table that both Qt and QML can reference--though I'm not sure how much linguist likes that--which should give us a way to keep language consistent (use frozen-map).

TODO: Docs for Qt stuff

Co-authored-by: MaranBr <maranbr@outlook.com>
Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/94
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Shinmegumi <shinmegumi@eden-emu.dev>

src/qt_common/qt_common.h

@@ -0,0 +1,44 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef QT_COMMON_H
+#define QT_COMMON_H
+
+#include <QWindow>
+#include "core/core.h"
+#include "core/file_sys/registered_cache.h"
+#include <core/frontend/emu_window.h>
+#include <memory>
+
+#include <core/file_sys/vfs/vfs_real.h>
+
+namespace QtCommon {
+
+#ifdef YUZU_QT_WIDGETS
+extern QWidget *rootObject;
+#else
+extern QObject *rootObject;
+#endif
+
+extern std::unique_ptr<Core::System> system;
+extern std::shared_ptr<FileSys::RealVfsFilesystem> vfs;
+extern std::unique_ptr<FileSys::ManualContentProvider> provider;
+
+typedef std::function<bool(std::size_t, std::size_t)> QtProgressCallback;
+
+Core::Frontend::WindowSystemType GetWindowSystemType();
+
+Core::Frontend::EmuWindow::WindowSystemInfo GetWindowSystemInfo(QWindow *window);
+
+#ifdef YUZU_QT_WIDGETS
+void Init(QWidget *root);
+#else
+void Init(QObject *root);
+#endif
+
+const QString tr(const char *str);
+const QString tr(const std::string &str);
+
+std::filesystem::path GetEdenCommand();
+} // namespace QtCommon
+#endif