Unify the interface to set cipher support for all services, and provide custom cipher support

The list of HIGH, MEDIUM, LOW ciphers keep changing based on vulnerabilities found. Today there is no way to specify a custom cipher list to support by each component instead the COUCHBASE_SSL_CIPHER_LIST can only be set to LOW, MEDIUM, HIGH

These SET LEVELS (LOW, MEDIUM,HIGH) are a moving target as vulnerabilities keep getting found, would be better to allow specifying a comma separated list of CIPHERS instead.