feat: Improvements about zoom scale value and ultra-wide camera

[ryuta46]

This PR is for improvements zoom scale feature, especially for avoiding to select ultra wide camera unintentionally. Please review and merge if looks good.

New features

• added zoomScale value notifier in MobileScannerController for the application to know the zoom scale value set actually.
  The value is notified from the native SDK(CameraX/AVFoundation).

• added resetZoomScale() in MobileScannerController to reset zoom ratio with 1x.
  Both Android and iOS, if the device have ultra-wide camera, calling setZoomScale with small value causes to use ultra-wide camera and may be diffcult to detect barcodes.
  resetZoomScale() is useful to use standard camera with zoom 1x.
  setZoomScale() with the specific value can realize same effect, but added resetZoomScale for avoiding floating point errors.
  The application can know what zoom scale value is selected actually by subscribing zoomScale above after calling resetZoomScale.

Changed behaviors

• (iOS only) call resetZoomScale while starting scan.
  Android camera is initialized with a zoom of 1x, whereas iOS is initialized with the minimum zoom value, which causes to select the ultra-wide camera unintentionally ([iOS] Impossible to focus and scan the QR code due to picking the wide back camera #554).
  Fixed this issue by calling resetZoomScale

• (iOS only) remove zoom animation with ramp function to match Android behavior.

[juliansteenbakker]

Thanks! LGTM!

[kgaulin]

hi, the title check is red. When this PR will be in a new version ? thank you