Fix svg scaling in iced_tiny_skia

[semiversus]

This pull request fixes two issues when tiny-skia is used and DPI scaling factor is unequal to 1.0.

• scaling factor of svg images is wrong (see issue SVG DPI scaling issue with tiny-skia #2825)
• svg images are getting pixelated when scaling (you also see it in issue SVG DPI scaling issue with tiny-skia #2825)

Changes done to fix these issues:

• Vector pipeline .draw gets physical_bounds but needs *bounds
• The SVG is rendered with size defined by logical size and then the pixmap is scaled up. Change this to rendering in physical size.
• Arguments with _ prefix get the prefix removed, as the arguments are used.

Fixes #2825.

[semiversus]

Using the minimal repo from @njust (https://github.com/njust/iced-svg-issue) here are the results:

Scale 1.0

Scale 2.0 (with original 1.13.1)

Scale 2.0 with this fix

[hecrj]

Thanks!

I'm fairly sure this breaks rotation, but it's better than the current implementation.

Also, the _ prefix is needed because both the image and svg features may be disabled.