[3.10] gh-99146 struct module documentation should have more predictable examples/warnings (GH-99141) (GH-99703)

gh-99146 struct module documentation should have more predictable examples/warnings (GH-99141)

* nail down a couple examples to have more predictable output

* update a number of things, but this is really just a stash...

* added an applications section to describe typical uses for native and machine-independent formats

* make sure all format strings use a format prefix character

* responding to comments from @gpshead. Not likely finished yet.

* This got more involved than I expected...

* respond to several PR comments
* a lot of wordsmithing
* try and be more consistent in use of ``x`` vs ``'x'``
* expand examples a bit
* update the "see also" to be more up-to-date
* original examples relied on import * so present all examples as if

* reformat based on @gpshead comment (missed before)

* responding to comments

* missed this

* one more suggested edit

* wordsmithing
(cherry picked from commit 22d91c16bb03c3d87f53b5fee10325b876262a78)

Co-authored-by: Skip Montanaro <skip.montanaro@gmail.com>

Co-authored-by: Skip Montanaro <skip.montanaro@gmail.com>