github: Fix and simplify kernel-apply-patch.sh regarding hv-daemons

[chewi]

Fix and simplify kernel-apply-patch.sh

See #3565.

This action is kicked off from main for all channels, but the script is run against each branch, so we can assume that hv-daemons is there.

COREOS_SOURCE_REVISION isn't in the hv-daemons ebuild, but that doesn't matter. sed will do nothing.

How to use

You can probably run kernel-apply-patch.sh manually.

Testing done

I tested the changed snippet manually:

chewi@ignea ~/Projects/flatcar/scripts $ NEW_VERSION=9.9.9
chewi@ignea ~/Projects/flatcar/scripts $ cd sdk_container/src/third_party/coreos-overlay

chewi@ignea ~/Projects/flatcar/scripts/sdk_container/src/third_party/coreos-overlay $ for pkg in sys-kernel/coreos-{sources,modules,kernel} app-emulation/hv-daemons; do
    pkg+=/${pkg##*/}
    git mv "${pkg}"-*.ebuild "${pkg}-${VERSION_NEW}.ebuild"
    sed -i -e '/^COREOS_SOURCE_REVISION=/s/=.*/=""/' "${pkg}-${VERSION_NEW}.ebuild"
done

chewi@ignea ~/Projects/flatcar/scripts/sdk_container/src/third_party/coreos-overlay $ git status .
On branch main
Your branch is up to date with 'origin/main'.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        renamed:    app-emulation/hv-daemons/hv-daemons-6.12.62.ebuild -> app-emulation/hv-daemons/hv-daemons-9.9.9.ebuild
        renamed:    sys-kernel/coreos-kernel/coreos-kernel-6.12.62.ebuild -> sys-kernel/coreos-kernel/coreos-kernel-9.9.9.ebuild
        renamed:    sys-kernel/coreos-modules/coreos-modules-6.12.62.ebuild -> sys-kernel/coreos-modules/coreos-modules-9.9.9.ebuild
        renamed:    sys-kernel/coreos-sources/coreos-sources-6.12.62.ebuild -> sys-kernel/coreos-sources/coreos-sources-9.9.9.ebuild

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update) -- N/A
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc. -- N/A