Fix strtoul test on alpine/musl

Fix strtoul test on alpine/musl

The strtoul tests that were recently added had a compile time check for
__WORDSIZE to properly determine the string to use for an maximal
unsigned long.  Unfortunately musl libc doesn't define __WORDSIZE so we
were in a position where on that platform we fall to the 32 bit unsigned
long variant, which breaks on x86 platforms.

Fix it by doing a preprocessor comparisong on ULONG_MAX instead.

NOTE: This works because preprocessors do arithmetic evaluation on
macros for every compiler we support.  We should be wary of some more
esoteric compilers though.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
(Merged from https://github.com/openssl/openssl/pull/24974)