info view: add xtriggers

List xtriggers in the info view.

This should display similar information to cylc show.

Here's an example snippet of cylc show output for a task with a retry xtrigger:

other: ('⨯': not satisfied)
  ⨯ xtrigger "_cylc_retry_30000105T0000Z/retry = wall_clock(trigger_time=2025-03-14T17:18:57,249741Z)"

And another with a wallclock xtrigger:

other: ('⨯': not satisfied)
  ⨯ xtrigger "wall_clock = wall_clock(trigger_time=3000-01-01T00:00:00Z)"

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