[Camera] Support setting exposure compensation to back and front camera (Both Android and iOS)

[iNima]

Description

This PR will add support for setting exposure compensation in real-time while the image/video is streaming via camera viewport.
It has added three main methods to the camera plugin which are:
getMinExposureCompensation() // minimum exposure compensation range for the current camera
getMinExposureCompensation() // maximum exposure compensation range for the current camera
applyExposureCompensation({int exposureValue = 0}) // apply the exposureValue to the current camera

We can use the min and max values to know the range of our slider or any other UIs that we are going to use for setting the exposure compensation.
The initial value for the exposure compensation is 0.
If the input parameter of the applyExposureCompensation is lower than the minimum or higher than the maximum of the target bias, the value will be mapped to the nearest range value (min/max). So, it wouldn't be set to a value out of the supported range.

I added a slider to the example app for setting exposure compensation value.
The main usage of this change would be for changing the brightness of the camera view.

Related Issues

Fixes flutter/flutter#24575
Fixes flutter/flutter#31225
Fixes flutter/flutter#41565

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Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

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[iNima]

@googlebot I signed it!

[mvanbeusekom]

Closing this PR as duplicate of #3346

[iNima]

Hi @mvanbeusekom
I don't know why it is considered as a duplicate to #3346.
This PR is related to set the exposure compensation regardless of the region or point which works similarly to change the brightness of the camera preview to a specific value. It is not auto exposure or based on the region or point.

[mvanbeusekom]

Hi @iNima,

Thank you for reaching out. PR #3346 also implements methods for setting the exposure compensation and checking the code base it is implemented similar to this PR. Are you missing any specific things? Am I overlooking something?