remove parent POM spoon-parent

[monperrus]

The semantics of parent POM in Maven is low understood, error-prone and conflicts with proper continuous delivery.

I propose to remove spoon-parent from spoon-core, which simply means copying the required dependencies in the main pom.xml.

Advantages:

• good software engineering with low coupling
• spoon-core does not depend on SNAPSHOTS (see chore: ensure in CI that there is no dependency to snapshots #5395)
• easier CD and testing (fix Failed to read artifact descriptor for Spoon 10.4.1-SNAPSHOT #5340)

We would first remove it from spoon-core and later for submodules.

[raghav-deepsource]

Does anything but spoon core still depend on spoon parent?