Add back getArgument(int, Class) to circumvent compilation issues

Also add `@NotExtensible` to several of our interfaces to document they
are not intended to be subclassed.

Fixes #1609

src/main/java/org/mockito/MockSettings.java

@@ -44,6 +44,7 @@
  * Firstly, to make it easy to add another mock setting when the demand comes.
  * Secondly, to enable combining together different mock settings without introducing zillions of overloaded mock() methods.
  */
+@NotExtensible
 public interface MockSettings extends Serializable {
 
     /**

src/main/java/org/mockito/MockitoFramework.java

@@ -20,6 +20,7 @@
  * @since 2.1.0
  */
 @Incubating
+@NotExtensible
 public interface MockitoFramework {
 
     /**

src/main/java/org/mockito/MockitoSession.java

@@ -88,6 +88,7 @@
  * @since 2.7.0
  */
 @Incubating
+@NotExtensible
 public interface MockitoSession {
 
     /**

src/main/java/org/mockito/internal/invocation/InterceptedInvocation.java

@@ -119,6 +119,11 @@ public <T> T getArgument(int index) {
         return (T) arguments[index];
     }
 
+    @Override
+    public <T> T getArgument(int index, Class<T> clazz) {
+        return clazz.cast(arguments[index]);
+    }
+
     @Override
     public Object callRealMethod() throws Throwable {
         if (!realMethod.isInvokable()) {

src/main/java/org/mockito/invocation/InvocationOnMock.java

@@ -7,13 +7,15 @@
 
 import java.io.Serializable;
 import java.lang.reflect.Method;
+import org.mockito.NotExtensible;
 
 /**
  * An invocation on a mock.
  *
  * <p>
  * A placeholder for mock, the method that was called and the arguments that were passed.
  */
+@NotExtensible
 public interface InvocationOnMock extends Serializable {
 
     /**
@@ -44,12 +46,35 @@ public interface InvocationOnMock extends Serializable {
      *
      * Can lookup in expanded arguments form {@link #getArguments()}.
      *
+     * This method is preferred over {@link #getArgument(int, Class)} for readability. Please read
+     * the documentation of {@link #getArgument(int, Class)} for an overview of situations when
+     * that method is preferred over this one.
+     *
      * @param index argument index
      * @return casted argument at the given index
      * @since 2.1.0
      */
     <T> T getArgument(int index);
 
+    /**
+     * Returns casted argument at the given index. This method is analogous to
+     * {@link #getArgument(int)}, but is necessary to circumvent issues when dealing with generics.
+     *
+     * In general, {@link #getArgument(int)} is the appropriate function to use. This particular
+     * function is only necessary if you are doing one of the following things:
+     *
+     * 1. You want to directly invoke a method on the result of {@link #getArgument(int)}.
+     * 2. You want to directly pas the result of the invocation into a function that accepts a generic parameter.
+     *
+     * If you prefer to use {@link #getArgument(int)} instead, you can circumvent the compilation
+     * issues by storing the intermediate result into a local variable with the correct type.
+     *
+     * @param index argument index
+     * @param clazz clazz to cast the argument to
+     * @return casted argument at the given index
+     */
+    <T> T getArgument(int index, Class<T> clazz);
+
     /**
      * calls real method
      * <p>

src/main/java/org/mockito/session/MockitoSessionBuilder.java

@@ -7,6 +7,7 @@
 import org.mockito.Incubating;
 import org.mockito.MockitoAnnotations;
 import org.mockito.MockitoSession;
+import org.mockito.NotExtensible;
 import org.mockito.exceptions.misusing.UnfinishedMockingSessionException;
 import org.mockito.quality.Strictness;
 
@@ -17,6 +18,7 @@
  * @since 2.7.0
  */
 @Incubating
+@NotExtensible
 public interface MockitoSessionBuilder {
 
     /**

src/main/java/org/mockito/session/MockitoSessionLogger.java

@@ -6,6 +6,7 @@
 
 import org.mockito.Incubating;
 import org.mockito.MockitoSession;
+import org.mockito.NotExtensible;
 
 /**
  * Logger for {@linkplain org.mockito.quality.MockitoHint hints} emitted when
@@ -17,6 +18,7 @@
  * @since 2.15.0
  */
 @Incubating
+@NotExtensible
 public interface MockitoSessionLogger {
 
     /**