Tracking Issue: Vello integration

[TrueDoctor]

### Tasks
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1848
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1858
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1849
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1850
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1851
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1864
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1866
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1867
- [ ] #1873
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1862
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1872
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1898
- [ ] #1904
- [ ] #1901
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1861
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1863
- [ ] https://github.com/GraphiteEditor/Graphite/issues/1895
- [ ] https://github.com/GraphiteEditor/Graphite/issues/2006
- [ ] https://github.com/GraphiteEditor/Graphite/issues/2007
- [ ] https://github.com/GraphiteEditor/Graphite/issues/2008
- [ ] https://github.com/GraphiteEditor/Graphite/issues/2034