Doughnut/Pie chart border radius

[etimberg]

Enables setting the borderRadius of arc elements (pie/doughnut charts). This can either be set as a single value, or an object specifying the radius for each corner. For the object, the keys are outerStart, outerEnd, innerStart, and innerEnd since I thought that topLeft, topRight, bottomLeft, and bottomRight would get confusing.

Resolves #3644
Resolves #5503
Resolves #6653

[etimberg]

I marked this as a draft for now so that we don't merge it until after v3.0.0 ships. It is ready for review

[etimberg]

Size Change: +1.51 kB (+1%)

Total Size: 234 kB

Filename	Size	Change
dist/chart.esm.js	67.9 kB	+574 B (+1%)
dist/chart.js	85.6 kB	+571 B (+1%)
dist/chart.min.js	61 kB	+355 B (+1%)
dist/chunks/helpers.segment.js	18.9 kB	+6 B (0%)
dist/helpers.esm.js	1.08 kB	+6 B (+1%)

[etimberg]

Based on the size increase, I'll need to go through and really try and squeeze it down. Now that tests are in, it should be easier.

[kurkle]

I think a test with really small radius, like 4 would be good to have too.

[etimberg]

Now at

Size Change: +1.66 kB (+1%)

Total Size: 235 kB

Filename	Size	Change
dist/chart.esm.js	67.8 kB	+510 B (+1%)
dist/chart.js	85.7 kB	+643 B (+1%)
dist/chart.min.js	61 kB	+358 B (+1%)
dist/chunks/helpers.segment.js	19 kB	+131 B (+1%)
dist/helpers.esm.js	1.1 kB	+21 B (+2%)

[kurkle]

Compressed size actually grew 🤔

[etimberg]

Getting rid of the repeating strings hurt gzip. If we compromised on the API and used the same border radius as others, then I could reduce a lot by getting rid of the second option parsing implementation.

[kurkle]

Size Change: +1.5 kB (+1%)

Total Size: 234 kB

Filename	Size	Change
dist/chart.esm.js	67.8 kB	+585 B (+1%)
dist/chart.js	85.6 kB	+573 B (+1%)
dist/chart.min.js	61 kB	+323 B (+1%)
dist/chunks/helpers.segment.js	19 kB	+11 B (0%)
dist/helpers.esm.js	1.1 kB	+13 B (+1%)

[kurkle]

[lint-js] /home/runner/work/Chart.js/Chart.js/src/elements/element.arc.js
[lint-js] 25:88 error Missing semicolon semi