* [core] initial implementation of high-level hashing infrastructure

* [core] apply rustfmt

* [core] add doc-comment to state some potential optimization

* [core] add Wrap as another built-in way of creating an InputBuffer instance

* [core] make &mut T implement InputBuffer if T: InputBuffer

* [core] publicly export Wrap

* [core] remove the two simple forms of all hash functions

* [core] add extensive docs with examples to all hash functions

* [core] fix doc tests

* [core] fix bug in InputBuffer impl of Wrap

* [core] add asserts to hash doc tests

* [core] apply rustfmt

* [core] simplify doc tests

* [core] adjust doc comments for raw hashes

* [core] improve docs

* [core] add missing internal docs

* [core] rename InputBuffer -> Accumulator

* [core] apply rustfmt

* [core] make Accumulator impl more explicit

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* [core] make Accumulator impl less explicit

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* [core] make Accumulator impl less explicit

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* [core] make Accumulator impl less explicit

Co-Authored-By: Nikolay Volf <nikvolf@gmail.com>

* [core] remove minor code dupe

* [core] completely refactor hash module

* [core] remove XX hash from low-level and high-level API

* [core] fix typo in docs

* [core] fix macro generated docs

Co-authored-by: Nikolay Volf <nikvolf@gmail.com>