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

[winddriver]

Thank you for contributing the cipher-list configuration code and for raising this use case.

We have now added explicit cipher-suite configuration APIs to ICrossSslSocket for both TLS versions:

• SetTls12CipherSuites(const ACipherRules: string) configures TLS 1.2 cipher rules through SSL_CTX_set_cipher_list.
• SetTls13CipherSuites(const ACipherSuites: string) configures TLS 1.3 cipher suites through SSL_CTX_set_ciphersuites.

The implementation also provides default cipher-suite constants for both versions and reuses the existing TLS configuration locking and error handling. The version-specific names make the scope of each API clear to callers.

Since this functionality is now covered by the implementation, we are closing this PR without merging its original branch.

Thanks again for your contribution and the code you shared!