[charts] Refactor tests to make it work in Highcharts V12

[DiegoCardoso]

Description

Currently, there are a few tests that fail when the Highcharts version is bumped to V12. If possible, they should be refactored such that they can work both for the current version and the V12. There might be cases where the changes between the versions won't make it possible to refactor the tests separately, but we should try to make the number of such cases as small as possible.

[DiegoCardoso]

The list of current tests failing once the Highcharts version is bumped to 12.

• packages/charts/test/exporting.test.js:

  • vaadin-chart exporting > should temporarily copy shadow styles to the body before export
  • vaadin-chart exporting > should remove shadow styles from body after export
  • vaadin-chart exporting > should add styled-mode attribute to body before export and delete it afterwards
  • vaadin-chart exporting > should not add styled-mode attribute to body if styledMode option

• packages/charts/test/chart-series.test.js:

  • vaadin-chart-series > markers > valid values > should not have markers when options are set
  • vaadin-chart-series > visibility toggling > should not hide on click when toggling is disabled
  • vaadin-chart-series > visibility toggling > should not show on click when toggling is disabled

• packages/charts/test/private-api.test.js:

  • vaadin-chart private API > __callHighchartsFunction > should be possible to modify all charts

• packages/charts/test/styling.test.js:

  • vaadin-chart styling > custom theme > should set series stroke applied with custom styles

• packages/charts/test/reattach.test.js:

  • reattach > should restore configuration done through updateConfigaration after reattach
  • reattach > should apply categories updated while detached after reattach
  • reattach > should apply xAxis min updated while detached after reattach
  • reattach > should apply xAxis max updated while detached after reattach

• packages/charts/test/chart-element.test.js:

  • vaadin-chart > height > should propagate height to the chart container
  • vaadin-chart > height > should update container height on chart resize
  • vaadin-chart > resize > should update chart width when container width changes
  • vaadin-chart > resize > should update chart height when container height changes