docgen now lists macro implementation status in the generated rst files.
Adds POSIX definition link property to docgen json API (`posix-definition`) and
changes the `defined` property of docgen json API to `c-definition`. Now that
docgen's api is getting more specified, adds validation checks to docgen to
start codifying the docgen api spec.
To make sure this all looks good, I've added POSIX definition links to signal.h
as a tester.
Closes#88066.
Compared to before, the function names in the stdbit table are sorted by
function name, not order-of-appearance in the standard. Since macros
aren't printed by docgen.py and are still a TODO in the code, they are
also not printed in the new stdbit.h docs.
Adds some checks to docgen.py for conditions that tripped me up.
Add code to docgen.py to add the include of the `|check|` rewriter,
since all other generated files need it.
