google-sargo: upgrade kernel and add firmware

This adds a new firmware package (and sub-package) and upgrades the kernel to a new release, based on 6.0.3.

For future reference, I might consider directly sourcing the firmware from the published OTA images using scripts from LineageOS. The modem firmware and vendor partitions can be mounted by grub-mount using FUSE (but should grub even be a makedepend?). The vendor partition is dynamic, so it might need lpunpack (which doesn't support multiple backing block devices yet as seen in sargo). This is all so the firmware can be extracted without root access, in an APKBUILD.