Create repack_gki, a standalone tool for repacking GKI images.

Bug: 191162695
Test: repack_gki --kernel_version 5.10 \
        --ramdisk_build_id <build id> --kernel_build_id <build id>
Test: unpack_bootimg for each individual boot.img.
      Ensure kernel images are replaced, and adhere to the following:
	- allsyms boot images use the debug (allsyms) kernel Image
	- gz boot images use the gz kernel Image
	- lz4 boot images use the lz4 kernel Image
Test: Repeat for boot images inside the
Test: Ensure BOOT/kernel-* inside match kernel build.
Change-Id: I0a3287ca83cb6e7b9739bfece4cffa1081272748
3 files changed