Add 2D canvas convenience method features

[ddbeck]

These are all a little small, but notable enough (e.g., see this web.dev write-up) and are all Baseline 2023 features:

• createConicGradient()
• roundRect()
• reset()

[foolip]

In addition to my name comment, would you mind landing #1081 and adding the group here too?

[foolip]

I find 10 reset() methods in webref, so this will need to be disambiguated. "Canvas reset()" would be most similar to "Canvas text baselines". I guess let's also do the same for all of these features?