Stop automatically pruning empty segments in RawPath

RawPath used to discard empty segments from lineTo/quadTo/cubicTo. However, it was still possible produce empty segments when transforming a path, and RawPath didn't catch those.

This change adds a simple utility, RawPath::pruneEmptySegments(), and passes the responsibility on to the client for using this method when necessary (including after a transform).

Diffs=
bae069339 Stop automatically pruning empty segments in RawPath (#5557)

Co-authored-by: Chris Dalton <99840794+csmartdalton@users.noreply.github.com>