Investigate sdk-swift framework enhancement

[amagyar-iohk]

The framework right now is integrated to XCTestCase lifecycle and some workarounds were needed.

This ticket is to investigate the possibility of using observers to control the lifecycle and queue the tests in a proper manner.

The goal of this ticket is to

1. Create a POC of test observer
2. Make a test executor
3. Report correctly if test fails
4. Improve overall stacktrace