Fix multiple iOS issues and add iOS compilation

[ihhub]

• move SDL2 and SDL2_Mixer under ios directory
• add a script to do automated downloads and unpacking
• add GitHub Actions pipeline support (for now just to make sure that we are able to compile)
• add a message when a user tries to exit the application. This prevents having a black screen after exiting within the game and also it is the way how iOS applications need to work
• add application icon
• remember configuration settings upon restarting the application
• preserve save files
• mark iPhone as a handheld device to avoid showing resolution selection
• make Virtual Keyboard as a default option for text input

relates to #10205

[ihhub]

Hi @oleg-derevenetz , I've added you as a reviewer since you handled GitHub Actions pipeline.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud