llvm: switch most targets to using half and fp128 IR types
As of LLVM 22, most backends can (finally) handle legalization of these types as
necessary, so we don't need to do it ourselves anymore.
closes https://github.com/ziglang/zig/issues/23674
1ad73c30fdAlex Rønne Petersen committed on 2/19/2026, 6:14:00 PMparent5a5aef1