Function interp_builtin_count 

fn interp_builtin_count(
    args: &[RValue],
    _named: &[(String, RValue)],
    _context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Return the number of builtins registered, optionally filtered by namespace.

This is a miniR extension — not in GNU R. Useful for debugging.

@param ns optional character scalar: namespace to filter by @return integer scalar @namespace base