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.
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.Checklist