Upgrade grub2 from 2.06 to 2.12

[CBL-Mariner-Bot]

Tested on local qemu-kvm install to virtual disk from 3.0 ISO installer (AMD64 and ARM64), as well as AMD64 SCHIE lab node installed to nvme disk (all not using secure boot). Tested secure boot on libvirt VM following TESTING from shim PR Confirmed TPM measurement with tpm2_eventlog and /sys/kernel/security/tpm0/binary_bios_measurements BuddyBuild pipeline ID 567570 FullBuild pipeline ID ?

[AUTOPATCHER-CORE] Upgrade grub2 to 2.12 fixes and features in latest full release, 2.06 is outdated Upgrade pipeline run -> https://dev.azure.com/mariner-org/mariner/_build/results?buildId=491222&view=results