Java 17 and Tycho 4

[LorenzoBettini]

Closes #225
Closes #215

Note that the older target has been upgraded to 2021-12 which is the first Eclipse version support Java 17. Photon is way too old and UI tests fail for JUnit 5 (it's useless trying to build with such an ancient version).

This PR also uses the new version of setup-java action.

[LorenzoBettini]

opps... I had forgotten to update the Tycho version in .mvn/extensions-xml; done that now

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[echebbi]

@LorenzoBettini I just noticed that our manifests are still requiring Java 1.8:

Bundle-RequiredExecutionEnvironment: JavaSE-1.8

Couldn't/shouldn't we upgrade to at least Java 11 as per our target platform? IIRC as of v2022-09 Eclipse's core bundles were already requiring Java 11 (maybe even Java 17 according to this page).

[LorenzoBettini]

@echebbi Yes, I always favored upgrading to newer Java, even Java 17. I seem to recall that you were reluctant to require newer Java versions as a minimal running environment ;)

Do you want me to address the move to Java 17 (or do you prefer Java 11?) in another PR?