Upstream indentation regexes to VS Code

[brettcannon]

Once #6497 lands we should upstream the appropriate regexes to https://github.com/microsoft/vscode/blob/master/extensions/python/language-configuration.json and delete https://github.com/microsoft/vscode/blob/master/extensions/python/src/pythonMain.ts so that all Python users benefit.

Steps

• Land Add regex to dedent else and friends #6497
• Write smoke tests to make sure upstream doesn't regress
• Upstream regexes to https://github.com/microsoft/vscode/blob/master/extensions/python/language-configuration.json
• Delete https://github.com/microsoft/vscode/tree/master/extensions/python/.vscode
• Delete https://github.com/microsoft/vscode/tree/master/extensions/python/src
• Delete https://github.com/microsoft/vscode/blob/master/extensions/python/tsconfig.json
• Delete our own code and tests

[brettcannon]

/cc @kimadeline

[luabud]

Closing as stale.