Add support for skipping propagation of TextEdit

[mickaelistria]

I'm trying to use JDT-LS directly inside the Eclipse IDE, as a thread (same VM, same workspace, same JDT-Core...).
When editing the document in the IDE, the change is then sent to the LS as a didChange notification. JDT-LS assumes it owns the document thus it transform the change back into a document edit and re-applies it; then the document receives a change notification and LSP4E will then send a new didChange for it, then JDT-LS re-applies the change on the doc, then...

[rgrunber]

Looks like the server only supports https://github.com/eclipse/eclipse.jdt.ls/blob/c9a2d051fc084f2d658c7326956c9698d12bee46/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/InitHandler.java#L180 currently. So we send the full text document on open, and incremental updates on changes.

There's an option for TextDocumentSyncKind.None. I wonder if we can make a configurable option for this (via. extended client capabilities sent on initialize) so that the server completely skips updating the document, and just goes directly to validation.

[mickaelistria]

Support for TextDocumentSyncKind.None seems to be the proper approach. It might actually require some updates on client side as well, but it's worth doing things proper.
I've updated the priorities and am currently starting with simpler approaches to start JDT-LS as a separate process for a first milestone; so this is not an immediate requirement. I'll come back to this issue when there is a stronger need for it.

[mickaelistria]

Current workaround: mickaelistria@57e38e3

[mickaelistria]

Suggested #2423

[mickaelistria]

Related PR: #2522

[mickaelistria]

Fixed with #2522