magit-section-show: reveal as much as possible
magit-{cherry-pick,revert}-read-args: new functions

replacing the shared `magit-sequencer-read-args'.
Revert "magit-section-show: reveal as much as possible"

This reverts commit 07ff8fec6b3ce0ba7dfea456f4a83b2b110fbb5d.
use singular for "diffstat"

Rename the section type `diffstats' to `diffstat',
rename `magit-jump-to-diffstats' to `magit-jump-to-diffstat', and
rename `magit-diff-wash-diffstats' to `magit-diff-wash-diffstats'.
magit-jump-to-diffstat-or-diff: new command

replacing `magit-jump-to-diffstat'.