Add viz settings to manage line style and thickness to line/area charts (#42043)

* Rename "Line style" to "Line shape"

* Add "line.style" viz setting

* Add "line.size" viz setting

* Apply new viz settings in line/area charts

* Clean up `ChartSettings` test suite

* Fix default values not applied

* Add visual test

* Add E2E test

* Rework default values

* Use constant S/M/L values for "line.size" setting