Use JUnit 5 for all tests

[aurelien-baudet]

• Use Junit5 for all tests
  • Use @DisplayName to explain what is tested
  • Wait for GreenMail Junit5 extension
  • Add JUnit 5 extensions for SmppServer
  • ogham-all: functional testing oriented test names (as developer...). Need to check if multiline is accepted
  • Update all dependencies to work with JUnit 5
  • Use @valuesource and other cool features that simplifies tests when possible
  • Replace ExpectedException by assertThrows

Currently GreenMail doesn't provide JUnit 5 extension (not published) and Spock doesn't support JUnit 5. Need also to test PIT testing