* Lower threshold for 2020 tests
Now that the tests zoom into the model and center it before taking a
snapshot, they should be less sensitive.
* Genuine, nontrivial changes to the integration test images
Previously these functions could not be used with `#[stdlib]` proc-macro:
```rust
fn someFn(data: &'a str) {}
fn someFn<'a>(data: Foo<'a>) {}
```
But now they can.
