Implement outlines for line renderer & use them for select & hover of "line-like" primitives in Viewer

[Wumpf]

Screen.Recording.2023-03-10.at.09.49.52.mov

Changing the outline mask for individual linestrips within a linebatch proved challenging. There's a bunch of conflicting requirements there:

• If everything changes mask, we don't want to re-upload data
• We ideally don't want to store a mask for every line strip even if they don't use it as this gets wasteful quickly
• We don't want to render everything again & discard in vertex shader if only a single/few linestrips are selected

The expectation is typically that either the entire batch or a few subranges are selected. Therefore, the solution chosen here is to have the mask be a property of the line batch, but allow emitting additional sub-batches that re-use the same data of their parent batch with a different outline mask.
This is unreasonably costly for many sub-ranges, but very cheap for the expected case. The sub-batch creation is done inside the LineRenderer, allowing us to adjust these details easier in the future.

Unfortunately, this still requires per-instance checks in the viewer - for the point renderer I should maybe come up with something else to avoid per-instance queries (also, point batches with single points seem non-sensical).

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)

[jleibs]

Looks good!