[Bug]: Different methods with same name are merged into one method

### Describe the bug

I use `spoon.refactoring.MethodInvocationSearch` to get the invocation relationship of methods, and different methods with same name are merged into one when i use `getInvocationsOfMethod` to retrieve the result. The demo is shown as below.

### Source code you are trying to analyze/transform

```Java
public class Test {

public void test2() {
test3();
Test2.test3();
Child.test3();
}

public static void test3() {

}

public void test4() {

}

private static class Child {
public static void test3() {

}
}

}
```

### Source code for your Spoon processing

```Java
@Slf4j
@RunWith(SpringRunner.class)
public class TestMethodLines {

@Test
public void test() throws URISyntaxException {
final Launcher spoon = initSpoon();
MethodInvocationSearch processor = new MethodInvocationSearch();
CtModel model = spoon.getModel();
model.getElements(new TypeFilter<>(CtExecutable.class)).forEach(processor::scan);

MethodCallGraph methodCallGraph = MethodGraphUtils.buildMethodCallGraph(processor.getInvocationsOfMethod());
Collection allMethods = methodCallGraph.getAllMethods();
for (MethodCallGraph.MethodNode methodNode : allMethods) {
Collection callerMethods = methodNode.getCallerMethods();
if (CollectionUtils.size(callerMethods) != 0) {
String join = JOINER
.join(Collections2.transform(callerMethods, new Function() {
@Override public Object apply(MethodCallGraph.MethodNode input) {
return input.getMethod().getMethodName();
}
}));
System.out.println(methodNode.getMethod().getMethodName() + " is called by " +join);
}
}
}

private Launcher initSpoon() throws URISyntaxException {
String path = Test1.class.getResource("/" + "Test.java").toURI().getPath();
final String[] arg = {
"-i", path,
"-o", "target/spooned/"
};

final Launcher launcher = new Launcher();
launcher.setArgs(arg);
launcher.run();
return launcher;
}
}
```

### Actual output

```Java
test3 is called by test2
```

### Expected output

```Java
rathen than showing only one single method "test3 is called by test2" ,three different methods of "test3" are called by test2
```

### Spoon Version

tried with 9.1.0 and 10.1.1

### JVM Version

11

### What operating system are you using?

tried both on Linux and Windows