This issue is automatically created based on existing pull request: #38493: Extend Observer declaration in events.xml by new attribute ifconfig

Description (*)

Extension of Observer declaration in events.xml by new optional attribute ifconfig with appropriate handling of it.
Similar to usage of ifconfig in layout's xml files - it executes (or not) Observer depending on boolean value of given config path. The purpose is to condition Observer's execution on config paths representing module's state - usually <module/general/active> or <module/general/enabled> etc.

Manual testing scenarios (*)

1. Add ifconfig attribute to Observer A declaration in events.xml file where its value will be config path and dispatch event to trigger Observer.
   a) When config path value equals to true - Observer should execute.
   b) When config path value equals to false - Observer should not execute
   c) When config does not exist (path does not represent any actual value) - Observer should not execute
2. Add ifconfig attribute to Observer A declaration in events.xml file where its value is empty string "" and dispatch event to trigger Observer. Observer should execute.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)