[Feature request] Support multiple ciphersuites in Bertie

[franziskuskiefer]

Is your feature request related to a problem? Please describe.
Clients usually don't know what ciphersuites the server supports and should therefore advertise and handle multiple ciphersuites.
Servers must support multiple ciphersuites as well in order to communicate with different clients.

Describe the solution you'd like
Allow setting multiple ciphersuites in client_connect and server_accept.

[jschneider-bensch]

#70 partially addresses this, in that it allows specifying algorithms on the CLI of clients and servers. It does not fully address the issue, since only one combination can be enabled at a time. For the client, this allows iterating over ciphersuites from the outside to test connectivity against a given server per suite.