No functional changes are made, and all APIs are moved to strictly less
restrictive bounds.

These APIs changed from the old bound listed to no trait bounds:

K: Hash + Eq
* new
* with_capacity

K: Eq + Hash, S: BuildHasher
* with_hasher
* with_capacity_and_hasher
* hasher

K: Eq + Hash + Debug -> K: Debug
S: BuildHasher -> S
<HashMap as Debug>

K: Eq + Hash -> K
S: BuildHasher + Default -> S: Default
<HashMap as Default>

No functional changes are made, and all APIs are moved to strictly less
restrictive bounds.

These APIs changed from the old bound listed to the new bound:

T: Hash + Eq -> T
* new
* with_capacity

T: Eq + Hash, S: BuildHasher -> T
* with_hasher
* with_capacity_and_hasher
* hasher

T: Eq + Hash + Debug -> T: Debug
S: BuildHasher -> S
<HashSet as Debug>

T: Eq + Hash -> T
S: BuildHasher + Default -> S: Default
<HashSet as Default>