Replace minimal-json dependency

minimal-json is unmaintained. Maybe come back to gson if there is no problem with OSGi

We should also take the opportunity to stop signing ourselves third party libraries like minimal-json, because we are not the owner of the code anyway. Also, we end up with the same version of minimal-json in different SonarLint repositories, but with a different signature.

For example:
https://binaries.sonarsource.com/SonarLint-for-Eclipse/releases/7.2.1.42550/plugins/minimal-json_0.9.5.jar signature expires on 2023-10-19
while
https://binaries.sonarsource.com/SonarLint-for-Eclipse/releases/6.1.0.36269/plugins/minimal-json_0.9.5.jar signature already expired on 2021-10-16
and we don't control the JAR that p2 will download.