Fix Line2 Raycasting bounds margin computation to support Orthographic Camera

[gkjohnson]

Related issue: #22782

Description

This PR adjusts the logic for computing the margin for the sphere and box bounds around Line2 to correctly (I believe) determine the world-space width of the thickness of the line at the closest point on the bounding sphere / box.

The logic for computing the margin is now encapsulated in getWorldSpaceHalfWidth. It now transforms a point at the given distance into clip space, adjusts the point by the pixel width / resolution, then transforms back into world space and returns the max of the xy values as the margin. Tested by copying the jsfiddle of the above issue into one of the fat_lines three.js example pages for local dev.

@nkallen can you test this?

cc @WestLangley

[mrdoob]

@WestLangley Looks good?

[nkallen]

I checked out this branch in my own codebase and the new behavior is good.

[WestLangley]

@WestLangley Looks good?

I trust @gkjohnson on this feature. :-)

[mrdoob]

Thanks!