[libc++] Various cleanups in the ranges tests

- Rename test files to follow conventions better
- Split constructor tests that were in a single file
- Add missing tests for take_view and transform_view's default constructors
- Add missing tests for transform_view's view/function constructor
- Fix include guards
- Mark some tests as being specific to libc++

Differential Revision: https://reviews.llvm.org/D108829