[libc++][NFC] Split up ranges.transform.pass.cpp

`ranges.transform.pass.cpp` takes ~42s to run on my machine, `ranges.transform.binary.pass.cpp` takes ~26s and `ranges.transform.unary.pass.cpp` takes ~2s.

Reviewed By: ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D141965