Check for existence of Nile or Cairo, and StarkWare's vscode-cairo

[Eric Lau]

• Check for the existence of Nile or Cairo commands, otherwise give an error (including mentioning to use a venv if needed)
• Give an error/warning if StarkWare's vscode-cairo is not installed
• Give an error if the installed version of StarkWare's vscode-cairo is older than cairo-compile -v

[Chen Wen Kang]

Can we also add support to protostar as one of the task in this issue? Been using that and would love to contribute for that too!