Rename chart 'dataLabels' to 'labels'; throw deprecation warning if the former is used.

[MadsBuchmann]

Which issue does this PR close?

This PR closes #1905

What is the new behavior?

The input property dataLabels has been renamed to labels:

• References in the documentation has been updated to reflect the renaming
• References in the code has been updated to reflect the renaming
• dataLabels still works but will throw a deprecation warning

Besides that, i also ended up removing some unused imports along with a bit of rewording and -formating of the documentation.

Does this PR introduce a breaking change?

• Yes
• No

Checklist:

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When the pull request has been approved it will be automatically merged to master via automerge.

[mictro]

A bit hard to read double ternary: Consider something along the lines:

const labelsToApply = labels;
if (!labelsToApply) {
// No labels supplied - autogenerate default labels for the chart.
labelsToApply = isStockType ? this.getDefaultStockLabels(datasets, this.locale) : this.createBlankLabels(datasets);
}

[MadsBuchmann]

Modified the suggestion to rely on a const instead of let as i prefer to use immutable variables when i can get away with it. It has been changed to:

    const labelsToApply = (() => {
      if (labels?.length > 0) return labels;
      else if (type === 'stock') return this.getDefaultStockLabels(datasets, this.locale);
      else return this.createBlankLabels(datasets);

    })();

[mictro]

LGTM
Jeg har lagt en lille kommentar du kan overveje....

[mictro]