Improve handling of SVG transform and Some refactors

[TonyCrane]

Motivation

ManimGL only supports matrix(...), scale(...), translate(...) transform, and doesn't support multiple transformation in a single transform property, which causes many issues.

For example

Code:

class Code(Scene):
    def construct(self):
        svg = SVGMobject("formula.svg", stroke_width=0).set_width(13)
        self.add(svg)

Result:

This pull request adds full support for all transforms in the svg standard, which are matrix translate scale rotate skewX skewY.
And refactors the parsing of the name and parameters of each transform by referring to https://github.com/cjlano/svg/blob/3ea3384457c9780fa7d67837c9c5fd4ebc42cb3b/svg/svg.py#L75.

Proposed changes

• Mmanimlib/mobject/mobject.py: allow Mobject.scale receive iterable scale_factor clip it with min_scale_factor
• Mmanimlib/mobject/svg/svg_mobject.py: replace warnings.warn with log.warning
• Mmanimlib/mobject/svg/svg_mobject.py: refactor SVGMobject.handle_transforms and add support for rotate and skewX skewY

Test

The current performance of the above example

Code:

class Code(Scene):
    def construct(self):
        svg = SVGMobject("formula.svg", stroke_width=0).set_width(13)
        self.add(svg)

Result:

rotate

Code:

class Code(Scene):
    def construct(self):
        svg = SVGMobject("test.svg")
        self.add(svg)

<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
  <rect width="300" height="100" transform="rotate(60)"/>
</svg>

Result:

skewX and skewY

Code:

class Code(Scene):
    def construct(self):
        svg = VGroup(
            SVGMobject("skewX.svg"),
            SVGMobject("skewY.svg")
        ).arrange(RIGHT)
        self.add(svg)

skewX.svg:

<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
  <rect width="300" height="100" transform="skewX(30)"/>
</svg>

skewY.svg:

<svg xmlns="http://www.w3.org/2000/svg" version="1.1">
  <rect width="300" height="100" transform="skewY(30)"/>
</svg>

Result:

[TonyCrane]

I added a new class _PathStringParser to parse the path string.
Because the A command receives three numbers and two flag (which can only be 0 or 1) and then two numbers, the path string may be like A1.0 1.0 0 11.1 which represents 1.0 1.0 0 1 1 0.1.

[TonyCrane]

@3b1b, this pull request is ready to be merged :)

[3b1b]

Thanks for doing this!