Rename ossl_sleep() to OSSL_sleep() and make it public

Rename ossl_sleep() to OSSL_sleep() and make it public

ossl_sleep() was implemented as a static inline function in internal/e_os.h,
using usleep() on Unix and Sleep() on Windows.  So far well and good.
However, it also has a fallback implementation for systems that do not have
usleep() or Sleep(), and that implementation happens to use ossl_time_now(),
which is a normal function, private to libcrypto, and is judged to be too
complex to sanely make into a static inline function.

This fallback creates a problem, because we do use ossl_sleep() in apps/ and
a few test programs in test/, and when they are linked with libcrypto in
shared library form, ossl_time_now() can't be found, since it's not publicly
exposed.

Something needs to give, and the easiest, and hopefully sanest answer is to
make ossl_sleep() a publicly exposed function, which requires a slight name
change.

Documentation and 'make update' result included.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Dmitry Belyavskiy <beldmit@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/19330)