FR-18338.3

[alex-minaiev-frontegg]

This PR was founded on https://frontegg.atlassian.net/browse/FR-18338 point 3

Created FronteggApp and FronteggAuth interfaces for separation interface and realization and provided to customers only necessary methods and properties to avoid accessing the inner implementation of methods and properties.

New Component:

1. FronteggAppService - implementation of FronteggApp interface.
2. FronteggInnerStorage - store all necessary information about SDK running (baseUrl, clientId, applicationId, etc.). Created to avoid using FronteggApp and FronteggAppService by SDK components.
3. FronteggAuthService - implementation of FronteggAuth interface.
4. FronteggAppLifecycle - separate object for listening to application Lifecycle Events. Created to encapsulate all data and methods responsible for AppLifecycle (encapsulation Principle of OOP).
5. FronteggRefreshTokenTimer - separate object for managing RefreshTokenTimer. Created to encapsulate all data and methods responsible for RefreshTokenTimer (encapsulation Principle of OOP).
6. Renamed RefreshTokenService with RefreshTokenJobService - to avoid confusion with SDK Services.
7. ReadOnlyObservableValue - using ObservableValue customer could change the value of ObservableValue. ReadOnlyObservableValue lock set ability of value.

[alex-minaiev-frontegg]

@frontegg-david I've added comments to main classes please check.