Reland "Split DisplayListBuilder into DlCanvas optimizer and DlOp recorder classes".

This patch (https://github.com/flutter/engine/pull/44718) was reverted in https://github.com/flutter/engine/pull/44968 due to issues discovered in internal testing. This issue tracks relanding it.