Support JS events when loading a panel.

[tim-schilling]

This fixes the problem of the Timer Panel not inserting the browser
timings section after being loaded via the HistoryPanel.

These events could be wired into to better render panels or support
a more dynamic toolbar and/or panel.

Fixes #1439

[matthiask]

I think I like it.

@jdufresne I requested a review because you added the new panel loading code; please feel free to skip this if you don't find the time or energy for a review!

[tim-schilling]

I was thinking more about this and I'm going to make a single event with a property that contains the panel id. It makes more sense than the event being the panel id. I can create a public function that does the boiler plater listener logic that does the basic filtering. It seems cleaner in my mind.

[codecov]

Codecov Report

Merging #1441 (6bd557c) into main (5a3ccd9) will increase coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1441      +/-   ##
==========================================
+ Coverage   86.33%   86.50%   +0.16%     
==========================================
  Files          34       34              
  Lines        1852     1852              
  Branches      260      260              
==========================================
+ Hits         1599     1602       +3     
+ Misses        181      178       -3     
  Partials       72       72              

Impacted Files	Coverage Δ
debug_toolbar/panels/__init__.py	95.38% <ø> (ø)
debug_toolbar/panels/profiling.py	89.28% <0.00%> (+2.67%)	⬆️

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[tim-schilling]

I changed the approach to put the responsibility of handling the async nature of a panel's scripts on the panel's script rather than toolbar.js. I also changed the functionality to operate on rendering rather than ajax loading. I figured this would be more flexible in the future.

These commits should be squashed before merging (if approved).

[matthiask]

This looks good I think. @tim-schilling Do you think it's ready to merge or is there anything left to do here?

[tim-schilling]

Thanks for the reviews folks. Squashed and merged in.