* Skeleton classes for SafetyNet and EventSurveys.

* Fix LINTs, test compile error.

* Remove lint breaking TODOs.

* Add SafetyNet requirement validation call to the attestation interface.

* Don't return salt/nonce, just offer the caller directly the PPACAndroid protobuf class.

* Add documentation, fix test build error.

* Add documentation, fix test build error.

* Add environment variables for data donation server and SafetyNet API key.

* Remove unused function.

* Fix EnvironmentSetupTest.kt

* Move AppConfig related code into it's own package.
* Use "files" instead of "cache" for storing our AppConfigApiTest.
* Add "files" to "cache" migration.
* Refactor CDN related code into an independent "environment module".

TODO: UnitTests, Fallback behavior even if cached AppConfig is stale.

* Further structure refactoring and unit test for app config cache migration.

* Added config fallback behavior for all cases + additional tests.

* Improve code readability.

* First POC for multi-environment support.

* logic for ACME test Countries toggle button in Dev menu

* ACME Test Countries dev menu

* Additional clean up and refactoring on build constants.

* Cleaned up the test fragment a bit.

* Fixed detekt issue

* Fix flaky test that depends on build variant.

* Let the test fragment show us the actual environment we toggled to.

* Changes upon review

* Address PR comments.

Co-authored-by: Rituraj Sambherao <git.rituraj.sambherao@gmail.com>