Refactor propagation of parsing errors for SVG attributes

Use the return value of SVG{...}::setValueAsString to signal errors
rather than an out parameter and the (mostly faux) ExceptionState
object (for setBaseValueAsString). In the few cases where the latter
is not using an TrackExceptionState - in tear-offs for SVGAngle and
SVGLength - it's easy enough to handle the exception-throwing there
and then.
This makes SVG{...} objects mostly independent of ExceptionState,
saving on footprint from string-construction and argument passing as
a side-effect.
Also remove some unnecessary virtuals on SVGInteger and
SVGPreserveAspectRatio.

BUG=231612

Review URL: https://codereview.chromium.org/1544673003

Cr-Commit-Position: refs/heads/master@{#366715}

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