cranelift-codegen: Expose EmitState and EmitInfo from aarch64 (#5640)

This commit exposes `EmitState` and `EmitInfo` so that they can be consumed by
Winch.

This is a follow up to https://github.com/bytecodealliance/wasmtime/pull/5570,
in which this should've been included.

cranelift/codegen/src/isa/aarch64/inst/mod.rs

@@ -21,7 +21,7 @@ pub mod imms;
 pub use self::imms::*;
 pub mod args;
 pub use self::args::*;
-pub(crate) mod emit;
+pub mod emit;
 pub(crate) use self::emit::*;
 use crate::isa::aarch64::abi::AArch64MachineDeps;