[SPv2] Rename TransformTreeManager to PropertyTreeManager.

I intend to use this for the clip tree, as well, and separating this from that
CL makes the diff easier to read. This CL has no functionality changes, just
mechanical renames.

BUG=563667

Review-Url: https://codereview.chromium.org/2122973002
Cr-Commit-Position: refs/heads/master@{#404013}
1 file changed