[WFCORE-5279/EAP7-1564] Split Elytron SSL into its own subsystem

[jessicarod7]

• https://issues.redhat.com/browse/EAP7-1564
• https://issues.redhat.com/browse/WFCORE-5279

Continuation from #371

[jessicarod7]

Updated the proposal to clarify some aspects of the scope, planned changes, and features, based on my better understanding of how components interact. Copying the commit messages below:

Clarified scope, updated elytron-tls-tool

Main body of the proposal has be updated to better reflect the scope of the subsytem (TLS only, no SASL/JASPI). Also details that the elytron-tls-tool should support interactive configuration, like add-user.

Refined proposal for command and config structure

The previous proposal discussed using both references and objects to store some elements (ex. key stores) within the subsystem. This makes it effectively incompatible with Elytron proper and also much harder to edit.

This updated proposal would only use "object attributes" for commands, but saved configuration will match that of Elytron as much as possible.