Lazy load the default project

[fbricon]

The default project is eagerly created every time jdt.ls is started, but it's only needed when working with standalone Java files. We should be able to create it only when needed.

Kinda similar to #1356

[rgrunber]

@fbricon , do you have the part of the code where this happens because I'm not seeing it started as part of JDT-LS startup.

I only see it in https://github.com/eclipse/eclipse.jdt.ls/blob/ed9d3c77ff9a6d0de6caf0813705d4c6a8aedab7/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/InitHandler.java#L244 => https://github.com/eclipse/eclipse.jdt.ls/blob/ed9d3c77ff9a6d0de6caf0813705d4c6a8aedab7/org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/managers/ProjectsManager.java#L106

but this happens on client initialize() call, and not JDT-LS activator startup.

[fbricon]

Yeah that's the one, happening before sending the "ready" status