x11/awww: Rename from x11/swww, update to 0.12.1, and unbreak

The upstream has moved from GitHub to Codeberg and renamed from swww
to awww.

Update to the latest version and unbreak build.

While here, add a patch to use std::process::Command for commmand
execution instead of Linux-specific rustix::runtime.

Changelog: https://codeberg.org/LGFae/awww/src/tag/v0.12.1/CHANGELOG.md

PR: 296847
Approved by: nivit (maintainer)