Fix several issues in wasm-c-api wasm_module_imports function:
1. Two of the if branches never set the module_name and name fields which are later passed as arguments to wasm_importtype_new, and eventually might cause double-free and/or use-after-free
2. Should zero module_name/name/extern_type at the start of loop iteration, and destroy their resources when failed at the end of loop iteration
2. No need to check `if (!extern_type) { continue; }`, as extern_type is converted from type and type is already checked
3. No need to wasm_importtype_vec_delete(out) when failed, as it is passed from outside and should be destroyed by outside
55ad4c7ec7