Prism: Fix the issue of timer clearing not working across bundle

[shunping]

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[lostluck]

Add a comment here saying "indicates this timer is being cleared". Also go to definition for the element struct definition, so we can update the documentation for the sequence about this usage of it: a value of -1 means this is a timer that should be cleared... etc.

[shunping]

Done.

[shunping]

Looking into the only failed test: PrismRunnerTest.test_pardo_timers_clear

[lostluck]

LGTM, let me know if you want me to look at anything else.

This is a very good find.

[github-actions]

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[shunping]

Thanks so much for reviewing this, @lostluck.

I will merge this first and work on a PR with the tests next.