fix(partition): linkLabel textColor override

[nickofthyme]

Summary

The partition chart type now respects the textColor defined on the config.linkLabels object. This will NOT adjust the color based on the background contrast.

Details

Added new ColorVariant key called Adaptive to be used in cases where color should be adaptive depending on the background contrast. Only when the the linkLabel.textColor is set to Adaptive, is the color contrast determined, otherwise the custom color string is used for all themes.

Also changed the eachTheme api to pass params without the & prefix, to be placed anywhere in the url.

---

Side note: I improved the error handling in the vrt framework. Before we waited for element from selector, if this failed, it would throw a misleading error that didn't help. Now if the element or url fails to load, there is an assertion to check the element exists and if not the test fails but does NOT throw an error. If the url fails to load the url will be logged to the console for easier debugging. See example below.

    fillLabel textcolor - treemap
      ✕ should show custom red textColor (10008 ms)

Docker Chromium: Shutting down Docker container...
  console.error
    Failed to load url. Check story at:

    	storybook url: http://localhost:9001/?path=/story/treemap--one-layer-2&knob-partitionLayout=sunburst&knob-custom fillLabel.textColor=true&knob-fillLabel.textColor=rgba(255, 0, 0, 0.85)
    	local vrt url: http://host.docker.internal:9002?path=%2Fstory%2Ftreemap--one-layer-2&knob-partitionLayout=sunburst&knob-custom%20fillLabel.textColor=true&knob-fillLabel.textColor=rgba(255%2C%200%2C%200%2C%200.85)&knob-debug=false

      441 |         return true;
      442 |       } catch {
    > 443 |         console.error(`Failed to load url. Check story at: \n\n\t storybook url: ${url}\n\tlocal vrt url: ${cleanUrl}`);
          |                 ^
      444 |         return false;
      445 |       }
      446 |     }

      at CommonPage.<anonymous> (page_objects/common.ts:443:17)
      at step (page_objects/common.ts:51:23)
      at Object.throw (page_objects/common.ts:32:53)
      at rejected (page_objects/common.ts:24:65)

Issues

fix #1469

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• All related issues have been linked (i.e. closes #123, fixes #123)
• New public API exports have been added to packages/charts/src/index.ts
• The proper documentation and/or storybook story has been added or updated
• Visual changes have been tested with all available themes including dark, light, eui-dark & eui-light

[nickofthyme]

FYI I came across #1499 while making these changes. So I added a VRT to test that in the future.

[markov00]

Thanks Nick, this change works for me. After removing the textInvertible property from the config some release ago, there was no more option to overwrite that computed value.
What do you think if we use the same technique also for the fill_label?

[nickofthyme]

What do you think if we use the same technique also for the fill_label?

Yeah I can add that

[nickofthyme]

Added suggested change in 74013ff. @markov00 could you do another review of the added changes please, thanks!