Enhance e2e test to support the introduction of new features

[jpraynaud]

Why

The e2e test is not working in the backward compatibility as soon as new features are introduced in a distribution which were not available before. This limits the accuracy of the nightly run of the backward compatibility test. We want to enhance the e2e test to support the introduction of new features in new distributions.

What

Support the introduction of new features in the e2e test and run associated tests only when necessary.

How

• Add a database of features introduced and the associated Mithril nodes and their versions
• Implement a mechanism that checks if a feature is available for a specific version of a Mithril node
• Adapt the specs tests for new features:
  • Retrieve the version of the Mithril nodes (by leveraging the --version of the binaries)
  • Check that the current version of the Mithril nodes are compatible
  • Run them if compatible
  • Display a info/warn message otherwise