[Amazon] StopConnect for UDC in Android tv-casting-app

Updated JNI and Android tv-casting-app to use CharToStringUTF
util function to create jstring and handle NULL JNIEnv interface

Changes
* JNI to use CharToStringUTF util function to create jstring for all
  ConnectionState and not just errors

Test
1. Manually verified UDC attempt is successful both Android iOS for following
   1. Attempt UDC attempt (both commissionee & commissioner generated passcode)
   2. Navigate back to discovery page
   3. Start new UDC attempt (both commissionee & commissioner generated passcode)

2. Manually verified UDC attempt is successful both Android iOS for following. UDC will finish in the background.
   1. Attempt UDC attempt (both commissionee & commissioner generated passcode)
   2. Confirm passcode on TV app or casting app depending on who
      generated passcode
   3. Navigate back before commission fnishes.

3. Manual regression test following
   * UDC attempt happy path (no navigate back) for both commissinee &
     commissioner generated passcode

Author: yuenton-amazon

examples/tv-casting-app/android/App/app/src/main/jni/cpp/core/MatterCastingPlayer-JNI.cpp

@@ -168,12 +168,14 @@ JNI_METHOD(void, disconnect)
 JNI_METHOD(jstring, getConnectionStateNative)
 (JNIEnv * env, jobject thiz)
 {
+    char error_str[50];
+    jobject jstr_obj = nullptr;
+
     if (NULL == env)
     {
-        jobject err_jstr = nullptr;
         LogErrorOnFailure(
-            chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString("JNIEnv interface is NULL"), err_jstr));
-        return static_cast<jstring>(err_jstr);
+            chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString("JNIEnv interface is NULL"), jstr_obj));
+        return static_cast<jstring>(jstr_obj);
     }
 
     chip::DeviceLayer::StackLock lock;
@@ -186,20 +188,20 @@ JNI_METHOD(jstring, getConnectionStateNative)
     switch (state)
     {
     case matter::casting::core::ConnectionState::CASTING_PLAYER_NOT_CONNECTED:
-        return env->NewStringUTF("NOT_CONNECTED");
+        LogErrorOnFailure(chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString("NOT_CONNECTED"), jstr_obj));
+        break;
     case matter::casting::core::ConnectionState::CASTING_PLAYER_CONNECTING:
-        return env->NewStringUTF("CONNECTING");
+        LogErrorOnFailure(chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString("CONNECTING"), jstr_obj));
+        break;
     case matter::casting::core::ConnectionState::CASTING_PLAYER_CONNECTED:
-        return env->NewStringUTF("CONNECTED");
-    default: {
-        char error_str[50];
+        LogErrorOnFailure(chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString("CONNECTED"), jstr_obj));
+        break;
+    default:
         snprintf(error_str, sizeof(error_str), "Unsupported Connection State: %d", state);
-
-        jobject err_jstr = nullptr;
-        LogErrorOnFailure(chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString(error_str), err_jstr));
-        return static_cast<jstring>(err_jstr);
-    }
+        LogErrorOnFailure(chip::JniReferences::GetInstance().CharToStringUTF(CharSpan::fromCharString(error_str), jstr_obj));
+        break;
     }
+    return static_cast<jstring>(jstr_obj);
 }
 
 JNI_METHOD(jobject, getEndpoints)