LSP: Running new extension side-by-side with old one

Both extensions should have access to VS options. We can put checkboxes there to say which features will be handled by new LSP extension and old extension will read it and not register its functionality for those.

Should be possible for the user to switch between LSP and non-LSP feature until we consider LSP stable. And we should be able to control the default value (be able to change the default for all users quickly).

Plus we need to make the LSP component work when it is packaged in the same vsix as our old extension.