feat(chart_state): add render change event

[nickofthyme]

Summary

Add render change (onRenderChange) lifecycle hook to Settings.

onRenderChange is a listener to be called when chart render state changes. isRendered value is true when rendering is complete and false otherwise.

Required to implement visualization count for Discover and TSVB.

http://localhost:9001/?path=/story/interactions--render-change-action

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• Any consumer-facing exports were added to src/index.ts (and stories only import from ../src except for test data & storybook)
• Proper documentation or storybook story was added for features that require explanation or tutorials
• Unit tests were updated or added to match the most common scenarios
• Each commit follows the convention

[codecov-io]

Codecov Report

Merging #365 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #365      +/-   ##
==========================================
+ Coverage   98.26%   98.27%   +<.01%     
==========================================
  Files          38       38              
  Lines        2772     2782      +10     
  Branches      654      656       +2     
==========================================
+ Hits         2724     2734      +10     
  Misses         44       44              
  Partials        4        4

Impacted Files	Coverage Δ
src/specs/settings.tsx	94.44% <100%> (+0.19%)	⬆️
src/chart_types/xy_chart/store/chart_state.ts	97.6% <100%> (+0.04%)	⬆️

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[monfera]

LGTM! The only small addition I wouldn't mind is an explanation of the significance of the true and false values that get emitted

[nickofthyme]

Good point I added the type here but an explanation would be good

elastic-charts/src/chart_types/xy_chart/store/chart_state.ts

Line 109 in 462b35a

export type RenderChangeListener = (isRendered: boolean) => void;

[nickofthyme]

@markov00 when you return, could you please look at this to see if the timing logic is correct?

I was thinking to put the trigger on the mount/update of the reactive_chart component but the timing was virtually identical to observing the chartInitialized value. Let me know what you think.

[markov00]

🎉 This PR is included in version 11.2.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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