Taper Stroke effect doesn't honor stroke-opacity

Summary:

When using the Taper Stroke LPE, the stroke-opacity attribute has no effect.

Steps to reproduce:

• open Inkscape
• draw a path
• set the stroke-opacity to 0.1
• apply the Taper Stroke LPE

What happened?

The path is once again fully opaque. Specifically, its opacity is now controlled by fill-opacity rather than stroke-opacity.

What should have happened?

The opacity should still be controlled by stroke-opacity.

This might be debatable since the LPE turns the stroke into a fill, but it seems less user-friendly this way. For example, I can select all objects with class .outline and adjust their stroke opacity, but it won't affect ones using this effect, and I can't just change opacity because that will change the fill too.

Version Info:

- Inkscape Version: Inkscape 1.2-dev (9a1a09f7b1, 2021-05-12, custom)
- Operating System: Artix x64
- Operating System version: N/A