## Summary
Resolves: https://github.com/elastic/kibana/issues/151463
Removes all reference to ephemeral tasks from the task manager plugin.
As well as unit and E2E tests while maintaining backwards compatibility
for `xpack.task_manager.ephemeral_tasks` flag to no-op if set. This PR
has some dependencies from the PR to remove ephemeral task support from
the alerting and actions plugin
(https://github.com/elastic/kibana/pull/197421). So it should be merged
after the other PR.
Deprecates the following configuration settings:
- xpack.task_manager.ephemeral_tasks.enabled
- xpack.task_manager.ephemeral_tasks.request_capacity
The user doesn't have to change anything on their end if they don't wish
to. This deprecation is made so if the above settings are defined,
kibana will simply do nothing.
### Checklist
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
5a9129e22d