feat: add SetCipherList to override TLS 1.2 cipher list

[freitasjca]

Summary

• Adds SetCipherList(const ACipherList: string) as a virtual; abstract method on TCrossSslSocketBase
• Implements it in TCrossOpenSslSocket via SSL_CTX_set_cipher_list, wrapped in the existing BeginTlsConfigUpdate/EndTlsConfigUpdate pair
• Empty string is a no-op (leaves the context default untouched)
• An unrecognised cipher string raises ESsl at call site rather than silently falling back

Motivation

Some deployments need to restrict TLS 1.2 to a custom cipher list (e.g. to comply with FIPS or PCI-DSS profiles) without forking the library. SetCipherList exposes the already-bound SSL_CTX_set_cipher_list through the public API.

Notes

• TLS 1.3 cipher suites are controlled separately by SSL_CTX_set_ciphersuites (not changed here)
• The existing SSL_CTX_set_cipher_list binding in Net.OpenSSL.pas is reused — no new import needed
• Follows the same pattern as SetCertificate, SetPrivateKey, and AddCACertificate