Prefer `Vec::extend_from_slice` over `Vec::extend` with `slice::to_vec`

What it does

Replace vec.extend(slice.to_vec()) with vec.extend_from_slice(slice)

Advantage

Saves making an uneccessary Vec (with a heap allocation and all that comes with it), and I think the resulting code is clearer

Drawbacks

No response

Example

let mut items = vec![1, 2, 3];
let slice = &[4, 5, 6];
items.extend(slice.to_vec());

Could be written as:

let mut items = vec![1, 2, 3];
let slice = &[4, 5, 6];
items.extend_from_slice(slice);

Comparison with existing lints

This feels similar to redundant_clone, and it might be reasonable to fold this under that lint instead of making a new one? I don't have strong feelings either way, just that clippy should lint on this case somehow

Additional Context

No response