Improvements to VSCode integration

Fixes:

• VSCode: Fix export of compile_commands.json (broken since CMake 3.17)
• VSCode: Improve Python/C++ intellisense by using per-folder settings (e.g. limit warnings from C++ extension)
• VSCode: Filter out PYTHONHOME from runtime environment

Improvements:

• VSCode: Default window title with full workspace path
• VSCode: Configure spell checker to be less intrusive (use hints not infos)
• VSCode: Disable telemetry to the vendor
• Update known issues in README

Internal changes:

• VSCode: Pin the python version used in utils
• Speed up setup-make.py