Add clippy rules to better align with #[no_std] #6380

I suggest the rules at:
https://rust-lang.github.io/rust-clippy/master/index.html?groups=restriction&search=instead_of

ATM it shows the following rules:

• clippy::alloc_instead_of_core
• clippy::std_instead_of_alloc
• clippy::std_instead_of_core