Package structured reworked for sealed packages

[wadoon]

This brings some clean-ups of the #3451 branch to main, without adding module-info.java files.

Features

• distinct packages for each (gradle) module
• fixing service loader files

Will break binary and source compatibility.

Future:

• module-info.java is currently not possible due to stringtemplate4.
• We might want to set an module name in the manifest to support auto modules.

[WolframPfeifer]

In general, I think it is a good idea to have disjoint packages for our (Gradle) submodules (i.e. key.core, key.ui, ...), even if we do not really use the module system at the moment.

Disabling the Ctrl+C signal handling is also fine, it was an experiment and apparently only worked correctly on some machines.

However, unfortunately there are the following blockers:

• Gradle task for GUI is not working, since build.gradle was not updated.
• Proof caching is completely disabled (?)

For a refactoring like this, I think you should have checked that everything works (at least a sanity check, i.e. running the KeY GUI once and see if the extensions are still there). In my opinion, this is not the task of the reviewer.

Minor remarks and open questions:

• Can you please update/complete the PR description? Otherwise, it is difficult to understand what this PR does exactly without looking into the code. Might also be relevant for the changelog ...
• I think the package name de.uka.ilkd.key.ui.core does not really make sense. Also, the separation between this, de.uka.ilkd.key.ui, and de.uka.ilkd.key.gui is not clear. If we are at restructuring, we should think of this as well.
• Is there any check/guarantee that the packages are actually disjoint now? It is really not obvious ...
• Can we prevent people from destroying disjointness accidentally in the future (for example, by adding a file in key.ui to package de.uka.ilkd.key.core)?

Thanks for the refactoring! If these points are resolved, it can be merged in my opinion.

[WolframPfeifer]

The caching extension is not available in the GUI any more. I think this is the reason ...

[WolframPfeifer]

Btw.: What do you mean by the label breaks API?

[wadoon]

Btw.: What do you mean by the label breaks API?

Breaks API indicates that a PR influences KeY's API and ABI. Hence, every downstream library, e.g., KeY4Eclipse, needs to be adopted---in this case, by changing the imports.