support react 19

[T4rk1n]

• Remove react 16 support.
• Add react 19 experimental support, use with:

from dash._dash_renderer import _set_react_version

_set_react_version("19.2.0")

[github-actions]

Thank you for your contribution to Dash! 🎉

This PR is exempt from requiring a linked issue due to its labels.

[AnnMarieW]

Thanks for supporting React 19 🎉

I see all the tests pass, but when I run apps setting react to 19.2.0 some components work (like dcc.Markdown and dcc.Input) but others do not, such as dcc.RangeSlider and the date picker components. The error is:

Cannot read properties of undefined (reading 'ReactCurrentOwner')

I see the same error if I set react 19 in the tests for those components.