Patch toml with tomllib

[whitphx]

tomllib was introduced since Python 3.11, so it's guaranteed to be available on stlite that uses the latest Pyodide version.
PyPI's toml is already disabled in stlite's Streamlit, so there is no drawback when we introduce such patching.
tomllib only provides load and loads but that should be sufficient for normal use of stlite. dump and dumps are only used in CLI commands.