5345 Make EJB timers nonpersistent

[poikilotherm]

What this PR does / why we need it:
As discussed in #5345, #7048, on IRC, Slack and Zoom plus this Google doc, we need to make the EJB timers non-persistent for enabling application-level database connection definitions.

Which issue(s) this PR closes:

Closes #5345

Special notes for your reviewer:

• It might me an idea to add a Flyway migration dropping the unused EJB timer table from the DB.

Suggestions on how to test this:

• Remember to reconfigure the EJB timer database (see release note)
• Check if timers still work.
• Check if timers still work on multi-instance installation without conflicting runs.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:
Nope.

Is there a release notes update needed for this change?:
Yeah, a small one about removing the EJB timer database configuration setting on the app server. 🔋 included.

Additional documentation:
This is a quick and dirty solution, not very sophisticated for future enhancements. At some point in the future, we need to come back to the ideas of the Google Doc.

[poikilotherm]

Like I said @landreev the actual code change is pretty trivial (2 lines). The rest is cosmetic and doc changes.

@landreev we might think adding a Flyway migration that deletes the old database table.

[coveralls]

Coverage remained the same at 19.48% when pulling 67172d7 on poikilotherm:5345-nonpersistent-ejb-timers into 9cce13d on IQSS:develop.

[scolapasta]

@pdurbin @landreev and I all took a look and we're happy with this one.

[poikilotherm]

Woohooo!

🌟 Thanks for merging @kcondon !!! 🌟