Fix update-pr-from-base-branch duplication

[yakov116]

1. LINKED ISSUES:
   Fixes Text from update-pr-from-base-branch is duplicated #3927

2. TEST URLS:
   Add conversation-timeline-filter feature #3847 (this needed 800)
   Shorten and fix separate-draft-pr-button #3922

3. SCREENSHOT:
   None

I went with debounce over select observer. My thinking was that this is the only issue.

[fregante]

Debounce delays the first API call by 800ms. Can you look into why the API call isn’t being cached? What event(s) is calling addButton 3 times?

[yakov116]

Looks like there are a few events that are happening. I could not figure them all out... So select-observer it is.

[fregante]

Can the observer’s selector be made more specific so we don’t have to use stillLoading? It should observe the final element that we need, it’s called once it’s found. No other listener should call addButton, selector observer is good specifically because we don’t have to deal with all kinds of listeners.

[yakov116]

Can the observer’s selector be made more specific so we don’t have to use stillLoading?

I think it could will check later tonight

[fregante]

Might be worth looking for a selector that also works on failing PRs #3699

[fregante]

I got an idea