🚧 Creates single threadpool to execute schedulers

[alecharp]

Description

Currently, multi scheduler can be executed at the same time. This means that we could be running the probe engine and updating the database at the same time.

Submitter checklist

• If the issue exists, it is well described and linked in the description
• The description of this pull request is detailed and explain why this pull request is needed
• The changeset is on a specific branch
  • feature/ for new feature, or improvements
  • fix/ for bug fixes
  • docs/ for any documentation changes
• If required, the documentation has been updated
• There is automated tests to cover the code change / addition
  • If there is no test, include an explanation why in the description
• Run mvn verify locally and all tests are passing successfully
  • It is OK to create a pull request which has failing tests if it is created as a draft, is to fix a bug and the first commit is the test to prove the existence of the bug.
• There is no new warnings (checkstyle nor spotbugs) on the code

[alecharp]

This has been open for far too long and is to much out of sync with the current content of the project