[libcxx] [test] Fix Clang -Wunused-local-typedef, part 1/3.
Mark typedefs as LIBCPP_ONLY when their only usage is within LIBCPP_STATIC_ASSERT.
test/std/containers/sequences/vector.bool/move_assign_noexcept.pass.cpp
test/std/containers/sequences/vector.bool/move_noexcept.pass.cpp
test/std/containers/sequences/vector.bool/swap_noexcept.pass.cpp
Additionally deal with conditional compilation.
test/std/containers/associative/map/map.cons/move_noexcept.pass.cpp
test/std/containers/associative/multimap/multimap.cons/move_noexcept.pass.cpp
Additionally deal with typedefs used by other typedefs.