perl_langinfo.h: Resume some assumptions

[khwilliamson]

To save some typing, I assumed that if a system had these glibc-only locale categories, that it would have all elements that comprise them. For example with LC_PAPER, the elements are the height and width of a piece of paper. It doesn't make any sense to have LC_PAPER without any dimensions available.

But Android has LC_PAPER without paper dimensions; the same with all the other elements in the glibc category extensions. See GH #22627.

I believe that means that these categories are useless on this platform.

But this commit now checks each element for existence individually; removing the assumption that if the category exists, the element must too.

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• This set of changes does not require a perldelta entry.

[jkeenan]

This p.r. is failing one test in the initial "sanity check" CI run: ../ext/I18N-Langinfo/t/Langinfo.t

# Failed test 92 - Returns expected value('ISO') for _NL_IDENTIFICATION_TERRITORY at t/locale.t line 237
#      got ""
# expected "ISO"
../ext/XS-APItest/t/locale.t ......................................... 
Failed 1/106 subtests 
	(less 5 skipped subtests: 100 okay)

Reproduced on a local build of this p.r. Also, as I noted in a different pull request, at the end of 'make test_prep' I'm getting a log of build-time warnings.