Copy-On-Write Vector Layers
This MR makes the KoShape hierarchy implicitly-sharable.
I'm not really sure on the steps besides the unit tests, but Krita's functions on vector layers should work the same as before. In particular, cloning and editing the shapes and/or layers should give out the same results as in master.
- I confirmed this builds.
- I confirmed Krita ran and the relevant functions work.
- I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
- I made sure my commits build individually and have good descriptions as per KDE guidelines.
- I made sure my code conforms to the standards set in the HACKING file.
- I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.