🚧 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
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• There is automated tests to cover the code change / addition
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• There is no new warnings (checkstyle nor spotbugs) on the code