Document effect of clearing a task instance on task state store

[amoghrajesh]

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Note on existing behaviour. It's this way because, we should attempt to connect to a remote job instead of submitting fresh even when cleared but its worth making a note of this.

Came up during review of #71211

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[jason810496]

IIUC, it only makes sense when the job is in the deferred state.
For the case of wait_for_termination=True + deferrable=False (watching the external job on worker instead of triggerer), we still execute the operator.on_kill hook, which result in killing the healthy external job and unable to connect back to the prior external job instance.

So perhaps we should mention the case of wait_for_termination=True + deferrable=True in the note? Just in case users interpret having ResumableJobMixin is same as "we can always connect to the external job after clear" but it's not.

[amoghrajesh]

@jason810496 thats a good point, I pushed an update. WDYT: f62d2d99fc?

[jason810496]

@jason810496 thats a good point, I pushed an update. WDYT: f62d2d9?

LGTM now, thanks for the update.