Change load_object_file to take a RelocationTarget instead of a LocalFunctionIndex.

This removes its last connection to the implementation details of having a wasm_module, which we don't want to have to rely on when building trampolines.

There currently isn't a RelocationTarget for a trampoline function that refers to itself (none of been observed to done so yet), so we make the RelocationTarget optional.

lib/compiler-llvm/src/translator/code.rs

@@ -279,7 +279,7 @@ impl FuncTranslator {
         load_object_file(
             mem_buf_slice,
             ".wasmer_function",
-            *local_func_index,
+            Some(RelocationTarget::LocalFunc(*local_func_index)),
             |name: &String| {
                 if let Some((index, _)) = func_names
                     .iter()