Unbind InputMethod when app crashes

If a running app (with bound InputMethod) crashes, the currently running InputMethod is not
unbound. As a result, onBindInput is not called.
In order to fix this, IMMS.removeClient() should also unbind the current client and clear
the flag IMMS.mBoundToMethod.
With the fix, I haven't seen any test failures mentioned in bug.

Bug: 72399950
Fixes: 73274813
Test: atest InputMethodServiceLifecycleTest && atest FocusHandlingTest
Change-Id: I0c09381b43a8b96480976edafbc0b0ee40ae5de0

services/core/java/com/android/server/InputMethodManagerService.java

@@ -1706,6 +1706,13 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
             if (cs != null) {
                 clearClientSessionLocked(cs);
                 if (mCurClient == cs) {
+                    if (mBoundToMethod) {
+                        mBoundToMethod = false;
+                        if (mCurMethod != null) {
+                            executeOrSendMessage(mCurMethod, mCaller.obtainMessageO(
+                                    MSG_UNBIND_INPUT, mCurMethod));
+                        }
+                    }
                     mCurClient = null;
                 }
                 if (mCurFocusedWindowClient == cs) {