egd: delete feature detection and related source code

egd: delete feature detection and related source code

EGD is Entropy Gathering Daemon, a socket-based entropy source supported
by pre-OpenSSL v1.1 versions and now deprecated. curl also deprecated it
a while ago.

Its detection in CMake was broken all along because OpenSSL libs were
not linked at the point of feature check.

Delete detection from both cmake and autotools, along with the related
source snippet, and the `--with-egd-socket=` `./configure` option.

Closes #11556