Extension ID renaming plan

[jcheng5]

In mid-May (when Joe gets back from vacation):

• [ ] Publish new extension under Posit.shiny
• [ ] Simultaneously, publish new version of Posit.shiny-python that removes all contribution points and depends on Posit.shiny, and rename to "[Deprecated] ..."
• [ ] Unpublish the very old, long-deprecated rstudio.pyshiny so we don't have two deprecated extensions showing up in search
• [ ] Review usage of Posit.shiny-python and PR the name change (e.g. Posit.shiny-python is a recommended extension in py-shiny)