Borrowed rstar CachedEnvelope container results in un-ergonomic code

[urschrei]

I was moving some geometries into a CachedEnvelope, and while fixing up the types found the following:

let p1: Point = (0., 1.).into();
let ce = CachedEnvelope::new(p1);
let bce = &ce; // pretend we're getting this out of a lending iterator
let p2: Point = (1., 1.).into();

p2.intersects(bce); // doesn't work
p2.intersects(*bce); // doesn't work
p2.intersects(**bce); // doesn't work
p2.intersects(&**bce); // FINALLY but look at that

Rust-Analyzer wasn't helpful here (which is fine) – you just "have to know" that you have to double-deref and then borrow again. Lots of people don't even know that you can double-deref.

Error messages in same order as above

error[E0277]: the trait bound `geo_types::Line<T>: algorithm::intersects::Intersects<CachedEnvelope<geo_types::Line<T>>>` is not satisfied
   --> geo/src/algorithm/simplify_vw.rs:429:39
    |
429 |             && new_segment.intersects(candidate)
    |                            ---------- ^^^^^^^^^ the trait `algorithm::intersects::Intersects<CachedEnvelope<geo_types::Line<T>>>` is not implemented for `geo_types::Line<T>`
    |                            |
    |                            required by a bound introduced by this call

error[E0308]: mismatched types
   --> geo/src/algorithm/simplify_vw.rs:429:39
    |
429 |             && new_segment.intersects(*candidate)
    |                            ---------- ^^^^^^^^^^ expected `&_`, found `CachedEnvelope<Line<T>>`
    |                            |
    |                            arguments to this method are incorrect
    |
    = note: expected reference `&_`
                  found struct `CachedEnvelope<geo_types::Line<T>>`
error[E0308]: mismatched types
   --> geo/src/algorithm/simplify_vw.rs:429:39
    |
429 |             && new_segment.intersects(**candidate)
    |                            ---------- ^^^^^^^^^^^ expected `&_`, found `Line<T>`
    |                            |
    |                            arguments to this method are incorrect

Anyway, I'm not sure what we can do about this – CachedEnvelope already impls Deref.