[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/android/app/src/main/res/values-ko/strings.xml

@@ -501,8 +501,6 @@
     <string name="use_custom_rtc">사용자 지정 RTC</string>
     <string name="use_custom_rtc_description">현재 시스템 시간과 별도로 사용자 지정 RTC를 설정할 수 있습니다.</string>
     <string name="set_custom_rtc">사용자 지정 RTC 설정</string>
-    <string name="disable_nca_verification">NCA 검증 비활성화</string>
-    <string name="disable_nca_verification_description">NCA 콘텐츠 아카이브의 무결성 검증을 비활성화합니다. 로딩 속도를 향상시킬 수 있지만 데이터 손상이나 유효하지 않은 파일이 미검증될 위험이 있습니다. 펌웨어 20+가 필요한 게임 및 업데이트를 실행하려면 필요합니다.</string>
 
     <!-- Network settings strings -->
     <string name="generate">생성</string>