Implement core::iter::Extend for storage collections (#341)

* Implement extend for Vec

* Implement extend for BinaryHeap

* Remove redundant core::iter imports

* Implement extend for BitVec

* Implement extend for BTreeMap

* Implement extend for HashMap

* Fmt

* Move trait bounds to where clause

* Cloned -> Copied

* More bounds moved to where clause

Co-authored-by: Hero Bird <robbepop@web.de>