Fix max timeout for open commissioning window

Commissioning window can be opened using timeout exceeding
the maximum value of 900 s defined by the spec. This can happen
if selected transport is IP, but the device uses BLE extended
announcement feature.

Added checking if device is commissioned to be able to determine
what max timeout should be used for the particular scenario.

Fixes: #35505

src/app/server/CommissioningWindowManager.h

@@ -61,12 +61,15 @@ class CommissioningWindowManager : public Messaging::UnsolicitedMessageHandler,
     static constexpr System::Clock::Seconds32 MaxCommissioningTimeout()
     {
 #if CHIP_DEVICE_CONFIG_BLE_EXT_ADVERTISING
-        // Specification section 2.3.1 - Extended Announcement Duration up to 48h
-        return System::Clock::Seconds32(60 * 60 * 48);
-#else
+        /* Allow for extended announcement only when device is uncomissioned. */
+        if (GetFabricTable().FabricCount() == 0)
+        {
+            // Specification section 2.3.1 - Extended Announcement Duration up to 48h
+            return System::Clock::Seconds32(60 * 60 * 48);
+        }
+#endif
         // Specification section 5.4.2.3. Announcement Duration says 15 minutes.
         return System::Clock::Seconds32(15 * 60);
-#endif
     }
 
     System::Clock::Seconds32 MinCommissioningTimeout() const