refactor: drop Boost.Move dependency

Implement constexpr definitions of forward and move to replace usage
of boost::move and boost::forward from the Boost.Move library.

Alter tests to use std::move instead of boost::move.

Remove the dependency on Boost.Move from build.jam

doc/90_dependencies.qbk

@@ -17,7 +17,6 @@ The implementation uses the following other Boost modules:
 # assert
 # config
 # core
-# move
 # static_assert
 # throw_exception
 # type_traits