ANativeWindow getWidth/Height does not detect any changes when using
Vulkan, so use the old onContentRectChanged callback to get notified
when size changed. Use those values instead when figuring out how large
swapchain to create.
Tested trivially on Galaxy S9+ Exynos model.
So this makes two basic changes:
1. Add a few extra dirs, hide root dir in the filesystem
2. Simplify the default dir selection code so it doesn't take three code blocks to change a dir
A few of the decisions here were weird.
This shouldn't affect anything for end users and makes the code more mantainable.
Log from the first run:
```
05-27 22:42:21.507 16529 16567 I RetroArch: jni_thread_destruct()
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV] Android version (major : 7, minor : 1, rel : 2)
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV] Checking arguments passed from intent ...
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: config file: [/storage/emulated/0/Android/data/com.retroarch.aarch64/files/retroarch.cfg] -->correct
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: current IME: [com.koushikdutta.vysor/.VysorIME]
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: libretro path: [/data/user/0/com.retroarch.aarch64/cores/]
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: android internal storage location: [/storage/emulated/0]
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: android picture folder location [/storage/emulated/0/Pictures] -->cleanup no longer needed
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: android download folder location [/storage/emulated/0/Download] -->cleanup no longer needed
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: APK location [/data/app/com.retroarch.aarch64-2/base.apk]
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: android external files location [/storage/emulated/0/Android/data/com.retroarch.aarch64/files]
05-27 22:45:27.586 16992 17046 I RetroArch: [ENV]: app dir: [/data/user/0/com.retroarch.aarch64]
05-27 22:45:27.586 16992 17046 I RetroArch: Testing permissions for /storage/emulated/0 -->correct
05-27 22:45:27.587 16992 17046 I RetroArch: Create /storage/emulated/0/.retroarch in /storage/emulated/0 true
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: application location: [/data/user/0/com.retroarch.aarch64]
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: default download folder: [] -->fixup
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: default savefile folder: [/storage/emulated/0/RetroArch/saves] -->correct
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: default savestate folder: [/storage/emulated/0/RetroArch/states] -->correct
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: default system folder: [/storage/emulated/0/RetroArch/system] -->correct
05-27 22:45:27.587 16992 17046 I RetroArch: [ENV]: default screenshot folder: [/storage/emulated/0/RetroArch/screenshots] -->correct
05-27 22:45:27.780 16992 17046 I RetroArch: [recording] youtube streaming key empty
05-27 22:45:27.781 16992 17046 W RetroArch: Using old --libretro behavior. Setting libretro_directory to "/data/user/0/com.retroarch.aarch64/cores/" instead.
05-27 22:45:27.781 16992 17046 I RetroArch: RetroArch 1.7.7 (Git 772d06f)
```
Also these are changed:
Should be easier to navigate to other mountpoints
