refact: enable NonNullByDefault for lsp4e.debug and lsp4e.jdt plugins

[sebthom]

No description provided.

[sebthom]

As part of this PR I had to copy parts of the org.eclipse.lsp4e.internal.NullSafetyHelper (located in the lsp4e plugin) to the lsp4e.debug plugin.
Copying code like this has been done before too: org.eclipse.lsp4e.debug.breakpoints.DocumentUtils only contains code copied from org.eclipse.lsp4e.LSPEclipseUtils.

@mickaelistria is there any real-world practical reason why lsp4e.debug should not depend on the lsp4e plugin to reuse these classes?

[mickaelistria]

is there any real-world practical reason why lsp4e.debug should not depend on the lsp4e plugin to reuse these classes?

IIRC, at the beginning, the goal was to get the Debug Adapter working for CDT without having LSP-based edition installed. It's the only case I'm aware of and I don't know if this still stands. @jonahgraham may know better.

[sebthom]

@rubenporras thanks for the quick review!

[jonahgraham]

IIRC, at the beginning, the goal was to get the Debug Adapter working for CDT without having LSP-based edition installed. It's the only case I'm aware of and I don't know if this still stands. @jonahgraham may know better.

Going forward there is no reason to keep them separate. CDT is moving to use LSP (https://github.com/eclipse-cdt/cdt-lsp) and there probably isn't an install anywhere that has lsp4e.debug and not main lsp4e.