Add the ability to make use of an automatically generated self-signed certificate with Elytron

WFCORE-1576 added the ability to lazily generate a self-signed certificate on first use for a specified host name when using legacy security. This RFE is to provide similar functionality when Elytron is in use. Like with legacy security, it will be important to log a warning message so the user knows that a self-signed certificate is being used and to indicate that this certificate should not be used in a production environment.