Pixel-perfect screenshot tests on different environments

[SimonMarquis]

While having pixel-perfect screenshots seems a good idea, it makes tests fail almost certainly on environments that are not 100% exact to the CI env.
Could we lower our expectations and restore the default changeThreshold (0.01F) in RoborazziOptions?

nowinandroid/core/screenshot-testing/src/main/kotlin/com/google/samples/apps/nowinandroid/core/testing/util/ScreenshotHelper.kt

Lines 42 to 43 in c4ebde1

	// Pixel-perfect matching
	compareOptions = CompareOptions(changeThreshold = 0f),

For example, running on Windows with jbr-17.0.7 leads to this output:

Roborazzi: GradientBackground_light_androidTheme_notDynamic.png The differ result :ComparisonResult(pixelDifferences=4, pixelCount=22500, width=150, height=150) changed:false
Roborazzi: GradientBackground_light_defaultTheme_dynamic.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=22500, width=150, height=150) changed:false
Roborazzi: Background_light_androidTheme_notDynamic.png The differ result :ComparisonResult(pixelDifferences=4, pixelCount=22500, width=150, height=150) changed:false
Roborazzi: FilterChipSelected_dark_androidTheme_notDynamic.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=12744, width=177, height=72) changed:false
Roborazzi: Navigation_fontScale2.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=73440, width=480, height=153) changed:false
Roborazzi: TopAppBar_fontScale2.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=46080, width=480, height=96) changed:false
Roborazzi: ForYouScreenPopulatedAndLoading_foldable.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=1175485, width=1009, height=1165) changed:false
Roborazzi: ForYouScreenPopulatedAndLoading_tablet.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=2119680, width=1920, height=1104) changed:false
Roborazzi: ForYouScreenPopulatedFeed_foldable.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=1175485, width=1009, height=1165) changed:false
Roborazzi: ForYouScreenPopulatedFeed_tablet.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=2119680, width=1920, height=1104) changed:false
Roborazzi: insets_snackbar_medium_medium.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=810000, width=900, height=900) changed:false
Roborazzi: insets_snackbar_expanded_expanded.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=1822500, width=1350, height=1350) changed:false
Roborazzi: snackbar_medium_medium.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=810000, width=900, height=900) changed:false
Roborazzi: snackbar_expanded_expanded.png The differ result :ComparisonResult(pixelDifferences=1, pixelCount=1822500, width=1350, height=1350) changed:false

As you can see, the pixelDifferences is generally very low, and we should probably allow some very slight variation, while still keeping the CI generated golden images as the single source of truth.

PS: There might be a good reason for it, but I did not find any mention of why pixel-perfect screenshots were configured in the first place: https://github.com/android/nowinandroid/pull/876/files#diff-4d54482e44efb1225f70ed9435e0c5da894e62592a8058f607ef7d3e22ba9e6dR35 If it is for CI purposes only, maybe we could switch behaviors based on env variables.