navigation should maintain token highlights

[psifertex]

When you navigate (including following a cross-reference for example), the token highlights should be maintained.

Right now if you follow a cross-reference, the previous token selection isn't maintained. This makes you lose visual anchoring of what you had selected.

Ultimately, it would be great if navigation via xref could navigate to the actual token itself and maintain the primary highlight selection but that requires a refactor of the navigation system so we'll see how well this much simpler change is at helping users maintain context when navigating before we consider that.

[psifertex]

cc: @juanandresgs