[select] Multiple select should support `FormData.getAll()`

[singpolyma]

Steps to reproduce

Look at https://github.com/mui/material-ui/blob/master/packages/mui-material/src/Select/SelectInput.js#L869 observe that it puts a comma separated value into the native input value

Current behavior

comma separated value in FormData

Expected behavior

Either multiple values (multiple inputs) or else nothing at all (so we can do it ourselves)

Context

Submit a form built using MUI

Your environment

No response

Search keywords: textfield selectinput multiple

[mj12albert]

I agree this should align more closely with how native form data behaves for multiple select, though it would be a breaking change

Workaround for now is to omit the name on select and render your own hidden inputs for form submission: https://stackblitz.com/edit/bfsls5uq?file=src%2FDemo.tsx