Small fixes for Android and iOS

[ivan-mogilko]

• Use FindFile class when searching for translations;
• Uniform DisplayAlert code.
• Use our Path functions when getting parent path.
• Add const to char* where makes sense.

Cannot test this on iOS myself.

On a side note, these likely could benefit from a MobilePlatform base class.

[ericoporto]

these likely could benefit from a MobilePlatform base class

I guess if one is written, it could go here: https://github.com/adventuregamestudio/ags/blob/master/Engine/platform/base/mobile_base.h

I wonder if the Display Alert could be in base itself and then we just delete it from the other places - maybe not the Windows one. It may need the parent window passed there for the desktop platforms instead of the nullptr.

I will review it on iOS later.

[ericoporto]

I verified this still works fine with the game! Here is an example of placing an empty game and having an error message appear, to demo the Display Alert

In a second run after removing the breakpoint