random: Remove remaining OpenSSL calls and locking infrastructure
Summary:
Partial backport of core PR17265:
https://github.com/bitcoin/bitcoin/pull/17265/commits/b49b6b0f7090cc15860d815fb0ef306ddfc718ba
Test Plan:
ninja all check-all
Run the Gitian builds.
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D6242