Fix CommissioneeDeviceProxy state

The pairing call was moved to external so the commissionee
device proxy never gets set to connected. LoadSecureSessionParameters
will take care of setting up the pairing in the session manager
so added a new function that gets called when the pairing is complete
to set the state and setup the pairing in the session manager.

src/controller/CHIPDeviceController.cpp

@@ -975,10 +975,9 @@ void DeviceCommissioner::OnSessionEstablished()
 
     // TODO: the session should know which peer we are trying to connect to when started
     pairing->SetPeerNodeId(mDeviceBeingCommissioned->GetDeviceId());
+    mDeviceBeingCommissioned->SetConnected();
 
-    CHIP_ERROR err = mSystemState->SessionMgr()->NewPairing(
-        mDeviceBeingCommissioned->GetSecureSessionHolder(), Optional<Transport::PeerAddress>::Value(pairing->GetPeerAddress()),
-        pairing->GetPeerNodeId(), pairing, CryptoContext::SessionRole::kInitiator, mFabricIndex);
+    CHIP_ERROR err = mDeviceBeingCommissioned->SetConnected();
     if (err != CHIP_NO_ERROR)
     {
         ChipLogError(Controller, "Failed in setting up secure channel: err %s", ErrorStr(err));

src/controller/CommissioneeDeviceProxy.cpp

@@ -132,6 +132,13 @@ CHIP_ERROR CommissioneeDeviceProxy::UpdateDeviceData(const Transport::PeerAddres
     return CHIP_NO_ERROR;
 }
 
+CHIP_ERROR CommissioneeDeviceProxy::SetConnected()
+{
+    mState = ConnectionState::SecureConnected;
+    bool didLoad;
+    return LoadSecureSessionParametersIfNeeded(didLoad);
+}
+
 void CommissioneeDeviceProxy::Reset()
 {
     SetActive(false);

src/controller/CommissioneeDeviceProxy.h

@@ -196,6 +196,14 @@ class CommissioneeDeviceProxy : public DeviceProxy, public SessionReleaseDelegat
 
     void SetActive(bool active) { mActive = active; }
 
+    /**
+     * @brief
+     * Should be called when the pairing completes.
+     *
+     * This causes the secure session parameters to be loaded and stores the session details in the session manager.
+     */
+    CHIP_ERROR SetConnected();
+
     bool IsSecureConnected() const override { return IsActive() && mState == ConnectionState::SecureConnected; }
 
     bool IsSessionSetupInProgress() const { return IsActive() && mState == ConnectionState::Connecting; }