Removes duplicate code in src/obj.rs, crates/obj and crates/jit/object.rs (#1993)

Changes:

 -  Moves object creation code from crates/jit/object.rs to the creates/obj (as ObjectBuilder)
 -   Removes legacy crates/obj/function.rs
 -  Removes write_debugsections

crates/jit/src/instantiate.rs

@@ -96,6 +96,12 @@ impl CompilationArtifacts {
             .collect::<Vec<_>>()
             .into_boxed_slice();
 
+        let obj = obj.write().map_err(|_| {
+            SetupError::Instantiate(InstantiationError::Resource(
+                "failed to create image memory".to_string(),
+            ))
+        })?;
+
         Ok(Self {
             module,
             obj: obj.into_boxed_slice(),