store mapping executed line <-> test cases

In some cases, we need to answer the question: which tests execute this line?

This information is not available easily 🤔.

To overcome this, we need to compute and store this data for each commit on master.

Good news, we already have the infrastructure for this 🚀:

* for each commit on master we run https://github.com/SpoonLabs/spoon-ci-external/
* with that, for each commit on master, we push on https://github.com/SpoonLabs/spoon-ci-data

Action: modify spoon-ci-external such that it also pushes the mapping line2tests to spoon-ci-data