Tracking issue for [T]::rchunks, rchunks_mut, rchunks_exact, rchunks_exact_mut

[SimonSapin]

Implemented in #54580.

These are similar to chunks, chunks_mut, chunks_exact, and chunks_exact_mut respectively, but they start from the end of the slice. They differ from calling .rev() on those other iterators (which is also possible) when the slice’s length is not a multiple of the chunk size: the remainder (either a smaller chunk or accessible through a separate method) is at the start of the slice instead of the end.

CC #47115 which tracks chunks_exact and chunks_exact_mut.

[sdroege]

Stabilization of this is in #55178 together with chunks_exact() and chunks_exact_mut()