Add `ellipse()` method to `SVGRenderingContext2D`

[IuryPiva]

Relates to #11337

In order to make Bokeh's SVG backend up to HTML Standard the arc function should use the ellipse implementation which is currently not defined.

[IuryPiva]

Ellipses on SVG and CanvasContext differs too much and have some clear limitations:

• SVG ellipse element is made of 4 different elliptical arcs https://www.w3.org/TR/SVG/shapes.html#EllipseElement each covering a quarter of the ellipse which can't be given start and end angles like CanvasContext' ellipse https://html.spec.whatwg.org/#dom-context-2d-ellipse
• Rotation happens in the origin for CanvasContext and on calculated center for SVG

Canvas left SVG Right

[mattpap]

Resolved in PR #11337.

[github-actions]

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