[libcxx][iterator] adds `std::ranges::prev`

Implements part of P0896 'The One Ranges Proposal'.
Implements [range.iter.op.prev].

Depends on D102563.

Differential Revision: https://reviews.llvm.org/D102564

NOKEYCHECK=True
GitOrigin-RevId: 0dc7fd1bc1670e9f7e58b08b51b478a6334c8b01
9 files changed