linux-postmarketos-qcom-sdm845: upgrade to 6.6.3 and enable ZBOOT

We're enabling ZBOOT to enable EFI booting with systemd-boot at some time in the future (this has no effect for current installs). This requires adjusting the packages as the output file is no longer Image.gz but just vmlinuz and linux.efi (compressed kernel with EFI boot stub). The EFI variant doesn't work with the stock bootloader, so we need to install both for compatibility with the current boot method and for booting via U-Boot in the future.

The EFI functionality (when added in the future) will require a change in mkinitfs to explicitly use the .efi variant, this patch only makes it available to simplify development and testing as we move towards switching to EFI booting by default.

The bootrr update ensures that bootrr failures will properly be detected by CI, no user-relevant changes.

Also get our 6.6 release out!

Already boot tested in CI on the OnePlus 6 and 6T (and booted manually on axolotl)

Please give this one a whirl folks!

• oneplus-enchilada (@Breakfastisready, @CarbonatedCaffeine, @susurrus, @antonok, @crowdtier, @PanzerSajt, @retourmy)
• oneplus-fajita (@susurrus, @fdlamotte)
• shift-axolotl (@antoniomaciej)
• xiaomi-beryllium (@anjandev, @PanzerSajt)