[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: eden-emu/eden#94
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Shinmegumi <shinmegumi@eden-emu.dev>

src/qt_common/externals/CMakeLists.txt

@@ -0,0 +1,20 @@
+# SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+include(CPMUtil)
+
+# Disable tests/tools in all externals supporting the standard option name
+set(BUILD_TESTING OFF)
+
+# Build only static externals
+set(BUILD_SHARED_LIBS OFF)
+
+# Skip install rules for all externals
+set_directory_properties(PROPERTIES EXCLUDE_FROM_ALL ON)
+
+# QuaZip
+AddJsonPackage(quazip)
+
+# frozen
+# TODO(crueter): Qt String Lookup
+AddJsonPackage(frozen)

src/qt_common/externals/cpmfile.json

@@ -0,0 +1,19 @@
+{
+    "quazip": {
+        "package": "QuaZip-Qt6",
+        "repo": "crueter/quazip-qt6",
+        "sha": "f838774d63",
+        "hash": "9f629a438699801244a106c8df6d5f8f8d19e80df54f530a89403a10c8c4e37a6e95606bbdd307f23636961e8ce34eb37a2186d589a1f227ac9c8e2c678e326e",
+        "version": "1.3",
+        "options": [
+            "QUAZIP_INSTALL OFF"
+        ]
+    },
+    "frozen": {
+        "package": "frozen",
+        "repo": "serge-sans-paille/frozen",
+        "sha": "61dce5ae18",
+        "hash": "1ae3d073e659c1f24b2cdd76379c90d6af9e06bc707d285a4fafce05f7a4c9e592ff208c94a9ae0f0d07620b3c6cec191f126b03d70ad4dfa496a86ed5658a6d",
+        "bundled": true
+    }
+}