cmake: detect `SSL_set0_wbio` in OpenSSL

cmake: detect `SSL_set0_wbio` in OpenSSL

Present in OpenSSL 1.1.0 and BoringSSL.
Missing from LibreSSL 3.8.0.

Follow-up to f39472ea9f4f4e12cfbc0500c4580a8d52ce4a59

While here, also fix `RAND_egd()` detection which was broken, likely all
along. This feature is probably broken with CMake builds and also
requires a sufficiently obsolete OpenSSL version, so this part of the
update was not tested.

Closes #11555