[5.2] Show show a warning when there are due tasks

[zero-24]

Summary of Changes

Show next run, show list by next run and show a warning when there are due tasks

Testing Instructions

• Load the scheduled tasks
• Notice the ordeing by title and the missing Next Run field from the list
• Apply this patch
• Open that page again
• Confrim that the Next Run field is there as well as its orderd by that field so the next task to run will be shown first

• Go to the database -> #__scheduler_tasks take one task and set the next_execution date to someting in the past
  

• Reload the scheduled tasks list and notice the message that comes up
  

• Use the "Test " button

• Notice the message is gone, it will come up of course as soon as there is another due task which is not run

Actual result BEFORE applying this Pull Request

No way to detect not run tasks or get to know the next tasks to trigger.

Expected result AFTER applying this Pull Request

1. Warning when there are due tasks
2. Option to show the next time a task should run
3. Default ordeing to show the next task to run first

Link to documentations

Please select:

• Documentation link for docs.joomla.org: https://help.joomla.org/proxy?keyref=Help51:Scheduled_Tasks&lang=en

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[Quy]

On initial load of list view, sort indicator does not match dropdown.

[zero-24]

Please try again @Quy

[richard67]

@zero-24 Is this a bug fix or a new feature?
If bug fix, then the bug may also apply to 4.4-dev and so should be fixed there, too (or only there and later be merged up to 5.1-dev). The bug might not be as visible on the 4.4-dev branch as it is here because in 4.4 we did not use the task scheduler for cyclic core stuff, but it might apply also there.
But if new feature: Shouldn't it be made for 5.2-dev?

[zero-24]

Moved to 5.2 looking forward to tests on this PR so it can be merged.