feat: create test framework for testing new storage implementations

[dgarus]

The module asto-core contains many universal storage tests StorageExtension.
We should allow using this tests to test new storage implementations.

We can create a new module asto-test, move common test classes to this module and
implement something like Reactive Streams TCK.

• move common storage tests to src (temporary, later it should be in a separate module)
• move S3Storage to separate module
• move EtcdStorage to separate module
• move VertxFileStorage to separate module
• fix VertxFileStorage verification tests for case root sub storage
• add verification test to asto-redis
• move ArtipieStorage to separate module
• document how to use verification tests