Version 6.0.0-beta17

refactor(): Rewrite how typeAssertion works to avoid isType and add tests for subclasses #9570
fix(): perform layout on poly change + initialization object subscription #9537
fix(): Addressing path cloning slowness ( partially ) #9573
fix(): exactBoundingBox stroke calculations #9572
feat(): Add save/restore ability to group LayoutManager #9564
fix(): Remove unwanted set type warning #9569
refactor(): Separate defaults for base fabric object vs interactive object. Also some moving around of variables #9474
refactor(): Change how LayoutManager handles restoring groups #9522
fix(BaseConfiguration): set devicePixelRatio from window #9470
fix(): bubble dirty flag for group only when true #9540
test() Backport a test to capture a failing text style situation #9531