[vector_graphics_compiler] fix: Stroke opacity not applied

[sysint64]

Fixes #158735

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[sysint64]

Related issues:

• currentColor opacity ignored dnfield/flutter_svg#617
• Stroke opacity not applied dnfield/flutter_svg#891
• [flutter_svg] currentColor opacity ignored flutter#158680

[jonahwilliams]

LGTM

Please correct the formatting issues so we can merge.

[sysint64]

@jonahwilliams Fixed