Run e2e tests on PR check with testing-prereleases

[odockal]

Please adjust a job on pr-check workflow to run e2e tests.

The main point is to use production testing-prerelease podman-desktop bits and avoid building it locally (can be used as fallback option).

Download latest GH release tar.gz from https://github.com/podman-desktop/testing-prereleases (ie.: https://github.com/podman-desktop/testing-prereleases/releases/download/v1.23.0-202510010133-214a0657ef6/podman-desktop-1.23.0-202510010133-214a0657ef6.tar.gz), extract it, find podman-desktop binary (maybe make it executable chmod +x xxx) and save the path into PODMAN_DESKTOP_BINARY env. var.

Then you can run e2e tests with prebuilt podman-desktop.