Chunk 9 of CMP contribution to OpenSSL: CMP client and related tests

Certificate Management Protocol (CMP, RFC 4210) extension to OpenSSL
Also includes CRMF (RFC 4211) and HTTP transfer

Chunk 9 of CMP contribution to OpenSSL: CMP client and related tests

Certificate Management Protocol (CMP, RFC 4210) extension to OpenSSL
Also includes CRMF (RFC 4211) and HTTP transfer (RFC 6712).
Adds the CMP and CRMF API to libcrypto and the "cmp" app to the CLI.
Adds extensive documentation and tests.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: David von Oheimb <david.von.oheimb@siemens.com>
(Merged from https://github.com/openssl/openssl/pull/11300)

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