Reworked GUI to support non-blocking UI and background download

[JayDi85]

Modal dialogs are special dialogs with exclusive focus. User can't clicks/press outside of the "window". Most required dialogs in xmage are modal, e.g. user must make a choice before continue. It's make dev life easy (no need in sync code) but has some limitations and other problems (see related issues below).

New system removed all modals (except few windows like Preferences) -- now it use non-blocking dialogs with callbacks. Dev must sync and control dialogs usage (create, show, process results and cleanup resources on close).

Full changes list:

• GUI: added non-blocking UI to almost all app and game dialogs;
• GUI: it allows to switch between UI dialogs and use any UI elements at any moment;
• GUI: it allows to use chat, card popup, battlefield, concede and other features while choosing (related to Add button to temporary hide all game dialogs #12670);
• GUI: it allows to download images while playing (related to UX improvements: background images downloading on first request #4160, not fully tested);
• GUI: enabled by default, can be disabled by java option: -Dxmage.guiModalMode=true
• connection: auto-connect will be visible in main menu on startup;
• connection: removed some unused features (auto-connect by command line);
• connection: added button to close connection dialog;
• download: added background images download (see non-blocking UI);
• download: improved cancel stability and fixes that it can't stop preparing/downloading process in some use cases;
• app: fixed freezes on macOS systems in some use cases (related to XMage is unusable on Mac M1 #12431, Client Freezes as Soon as it Starts up on MacOS #11292, Can’t run client on macOS (miss execute access to files) #9300, Mac Client freezes when launching new tourney #4920);