fix(runtime-c-api) wasmer_instance_call types matches wasmer_export_func_*_arity.

The `wasmer_export_func_params_arity` and
`wasmer_export_func_returns_arity` functions store the arity in a
`uint32_t`. The `wasmer_instance_call` expects `c_int`. There is a
type mismatch here. It's not annoying in C or C++, but in some other
languages that have bindings to C/C++, it can imply useless casting.

This patch changes `wasmer_instance_call` to expect `uint32_t` for
`params_len` and `results_len` to match the
`wasmer_export_func_*_arity` functions.

lib/runtime-c-api/src/instance.rs

@@ -125,9 +125,9 @@ pub unsafe extern "C" fn wasmer_instance_call(
     instance: *mut wasmer_instance_t,
     name: *const c_char,
     params: *const wasmer_value_t,
-    params_len: c_int,
+    params_len: uint32_t,
     results: *mut wasmer_value_t,
-    results_len: c_int,
+    results_len: uint32_t,
 ) -> wasmer_result_t {
     if instance.is_null() {
         update_last_error(CApiError {