RFC: Welch's ANOVA (unequal variances)

[zross]

Checklist

• [x] Read and understood the Code of Conduct.
• [x] Searched for existing issues and pull requests.
• [x] The issue name begins with RFC:.

Description

Sorry about a previous RFC for something that did exist in stdlib. I think I've done a better job here. I'm seeing ANOVA (anova1) but I'm not seeing a Welch's ANOVA (unequal variances). Perhaps adding this is a possibility?

For reference in R this is a oneway.test()

oneway.test(var1~grp, var.equal=FALSE)