Align web socket client implementation between Olog and save&restore

[georgweiss]

This is to align to the same web socket client implementation for Olog and save-and-restore. Server side has also been updated to use the same Spring Boot APIs.

New modules have been created to enable use of common APIs and thus reduce code duplication.

NOTE!!!
Sadly I had to change the Olog ES client implementation such that "Olog" is prepended to all endpoints. Reason is that the Olog service by default deploys to the context "/", but all endpoints start with /Olog. At the same time the Olog client (erroneously) handled this "Olog" prefix as the context root.
ACTION NEEDED
The preference setting org.phoebus.olog.es.api/olog_url must omit the "Olog" part of the URL!

Checklist

• Testing:

  • [ X] The feature has automated tests
  • [ X] Tests were run

• Documentation:

  • The feature is documented
  • The documentation is up to date
  • Release notes:
    • Added an entry if the change is breaking or significant
    • Added an entry when adding a new feature