Filter overload signatures from the results of getNavigationBarItems/getScriptLexicalStructure

[mhegazy]

This isn't really helping me choose where to navigate. There're 100s of results and they're not showing me any information I can use to distinguish these from one another (the file they're in, their type signature, etc).

[DanielRosenwasser]

This is at least partially fixed in #804 for navigate-to. Do we still want it for the navbar?

[danquirk]

The most likely scenario is that overload definitions are next to their implementation so even if the overloads in the nav bar had meaningful details to differentiate them from one another there's minimal value in cluttering up the list of functions with overload signatures. If the overloads don't have meaningful detail to differentiate one another then they certainly shouldn't be listed.

[DanielRosenwasser]

Just realized that we've always been collapsing declarations in the navbar, and it's more aggressive than navigate-to in that it also ignores non-consecutive overloads. Whether or not this is a consistency issue is another matter.