[MNG-7669] Add artifact-type for Tycho

[laeubi]

Since a while Tycho is going more and more "maven-like" so today even more Tycho artifacts approaching at maven-central.

In some circumstances this leads to strange problems, because Dependencies have a type (usually the packaging type) but artifacts have an extension (where different packaging types often map to the same extension), and maven only includes a few mappings by default users currently need to enable an extension so that this works.

This adds a new default mapping so this type can be used smoothly in maven.

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[michael-o]

I think this should be master first.

What about lifecycles?

[laeubi]

I think this should be master first.

I can create one for master as well, but if its not accepted for 3.9 it does not make much sense to port it (as master is a bit different one can't just cherry pick it from there).

What about lifecycles?

The problem only arise if maven tries to resolve an artifact, lifecycle is not affected.

[michael-o]

For me, this seems hardless. I'd like to know what others think. @gnodet @cstamas @hboutemy

[laeubi]

as @cstamas pointed out, only change in XML file would be required, I updated the PR.

[rmannibucau]

-1 for me to get anything not org.apache.maven in maven core, in particular when test covering is 0 and this can break any time.
+1 to get it maintained where it belongs to only.

[michael-o]

I wonder whether this could also be registered from .mvn/extensions.xml?! @cstamas WDYT?