XDomain should fallback to ordinal type

[nickofthyme]

Describe the bug
Using a LineSeries when defining an XScaleType as linear or undefined, elastic charts will try to use linear and use ordinal as a fallback if needed. This should be the same logic with AreaSeries.

Version (please complete the following information):

• OS: macOS
• Browser: chrome
• Elastic Charts: latest

Additional context
Related to code below...

elastic-charts/src/chart_types/xy_chart/domains/x_domain.ts

Lines 68 to 72 in a79e899

	if (!isNumberArray(values)) {
	throw new Error(
	`Each X value in a ${mainXScaleType.scaleType} x scale needs be be a number. String or objects are not allowed`,
	);
	}

Errors in browser console

Uncaught Error: Each X value in a linear x scale needs be be a number. String or objects are not allowed
    at Object.mergeXDomain (x_domain.js:51)
    at Object.computeSeriesDomains (utils.js:136)
    at compute_series_domains.js:14
    at resultFuncWithRecomputations (index.js:77)
    at index.js:70
    at index.js:30
    at index.js:84
    at index.js:30
    at selector (index.js:105)
    at index.js:80

[markov00]

🎉 This issue has been resolved in version 19.5.1 🎉

The release is available on:

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

Your semantic-release bot 📦🚀