[all] Proguard test rules

Hello,

When looking at the proguard rules I noticed that the `proguard-rules.pro` file contains a rules which keeps all the app classes and methods. Because some methods are only called from tests this is of course required but for release builds this seems unneeded to me. Is there a specific reason for this rule to be in the `proguard-rules.pro` file and not in the `proguardTest-rules.pro` file?

Compare the rules in proguard-rules.pro with the proposed proguardTest-rules.pro location, and determine why the app classes and methods are currently kept globally. Verify the effect on test and release builds; done means test-only rules are scoped appropriately without breaking either build.

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