Make sure "rename" doesn't show as an option on elements that can't be renamed

[luabud]

The issue was originally filed at https://github.com/microsoft/vscode-python/issues/10443 for Jedi. I just opened this here as well to make sure that it doesn't also happen with Pylance 😊

cc @savannahostrowski

Steps to reproduce:

1. In a python file, place cursor on None and try to rename it using F2
2. See input box
3. Enter a new name and press enter

Bug

See notification that says No result!

Here's what our builtin js/ts extension shows for this case (we show this before the input appears):

This is implemented using prepareRename: https://github.com/microsoft/vscode/blob/c0c9e0043ce6133042268f22847021ad9a1ce410/extensions/typescript-language-features/src/features/rename.ts#L34

[heejaechang]

this is a dup - #1360