[Tracker] Make the app lighter

[M123-dev]

What

We should make the app lighter (in parts) for easier development.

### Tasks
- [ ] Allow starting with a mock camera (which is always black)

Part of

• #2528

[Akashsri3bi]

Can you brief a little @M123-dev , then I start on this

[M123-dev]

@Akashsri3bi the camera is a core feature, but when developing on an emulator it just takes a lot of performance. So it would be good, to have a switch to deactivate the camera all together. Just showing a black screen where the camera would have been. (The overlay should stay)

[M123-dev]

Mainly for https://github.com/openfoodfacts/smooth-app/issues/2849

[monsieurtanuki]

@Akashsri3bi @M123-dev In that particular case I would recommend to wait for my new barcode scanner before starting any work. And if it's for me (#2849) that probably wouldn't help as the app would crash anyway.

[Akashsri3bi]

Okay @monsieurtanuki @M123-dev thanks for update!

[Akashsri3bi]

@M123-dev I think work can be started @monsieurtanuki just made the fix for barcode scanner

[monsieurtanuki]

@Akashsri3bi You should probably wait until the fix for barcode scanner is reviewed/approved/merged.

[Akashsri3bi]

@Akashsri3bi You should probably wait until the fix for barcode scanner is reviewed/approved/merged.

Yup ! Sure.