[libc++] Fix `take_view::__sentinel`'s `operator==` (#74655)

* Fix `take_view::__sentinel`'s `operator==`
* Rename `ranges/range.adaptors/range.take/sentinel/base.pass.cpp`
directory to
`ranges/range.adaptors/range.take/range.take.sentinel/base.pass.cpp`
* Add ***full*** test coverage for `take_view::__sentinel`'s
`operator==`
* Drive-by: fix comment in `base.pass.cpp` test
* Close #55211