terminology: treewide: Use "UEFI" rather than "EFI"

[phip1611]

[crawfxrd]

nits:

• Any legacy interfaces/types from/for EFI 1.10 should still use "EFI".
• Any user-facing interfaces/names that use "EFI" should continue to do so (e.g., "EFI System Partition"/"ESP" if it's used anywhere)