Motivation:
Due to https://bugs.swift.org/browse/SR-14516 , we sometimes get
allocating (!?) `subscript.read` accessors in the CircularBuffer.first
depending on the `Element` type...
Modifications:
Implement `CircularBuffer.first` instead of inheriting it from
Collection.
Result:
Fewer allocs in some cases.
Motivation:
Calling `function(otherFunction)` allocates, but
`function({ otherFunction($0) }` does not.
See: SR-12115 and SR-12116.
Modifications:
Avoid passing functions directly; pass them in new closures instead.
Result:
Fewer allocations.
Fabian Fett