Deprecate `ele.renderedStyle()`

[maxkfranz]

Issue type

Feature request

Description of new feature

Remove ele.renderedStyle() from the docs.

Motivation for new feature

• It returns a string value with units, so it is not ideal for getting numbers.
• It's redundant with ele.numericStyle(). Getting a rendered value is just a matter of multiplying by zoom level.

[maxkfranz]

Eventually for v4, the rendered value case can be removed from style.getStylePropertyValue(): #2221 #2019