feature: scan_progress

[m-schmoock]

It's helpful to track the scan progress state (focus, edge, vseg, hseg, stability...).
It enables additional functionality like visible user feedback guidance
or autofocus trigger once hseg is reached which I have also put
in the pull requests (dmz and android).

This increases user experience because:

• The user does not have to trigger autofocus manually by tapping on the display that may shake the device and decrease detection rate / user experience.
• The user gets visible feedback on 'how good' the card can be currently scanned by a progress bar and guide colors. This helps the user intuitively to hold the card in a way a successful scan is more likely/sooner to happen.

[m-schmoock]

I just realized that instead of introducing a new void scanner_frame_result(ScannerState *state, ScannerResult *result, FrameScanResult *frameResult) function we could also use the return value of void scanner_result() to be int SCAN_PROGRESS and put into the FrameScanResult from by the caller. This way we wouldn't have a temporary legacy function and no additional argument or null checks. The drawback would be to have implicit logic by the caller.

You can decide whats better...