[mle] enhance RLOC and ALOC address generation (#10391)

This commit enhances the generation of RLOC and ALOC addresses in the
`Mle` class.

Methods retrieving RLOC/ALOC addresses no longer return an `Error` and
are now `void`. The previous check for a valid `GetRloc16()` value,
which returned `kErrorDetach` if unset, is removed because this
scenario only occurred before the device's initial attachment.
Post-attachment, the RLOC16 remains valid even if the device is
detached. This change simplifies the code since RLOC/ALOC address
retrieval happens after the initial attachment.

Additional enhancements include:

-   Changing the input parameter order in `GetCommissionerAloc()` to
    match `GetServiceAloc()`.
-   Using `Ip6::Address::SetToRoutingLocator()` to construct RLOC
    addresses, harmonizing address generation and improving code
    readability.

src/core/thread/dua_manager.cpp

@@ -512,7 +512,7 @@ void DuaManager::PerformNextRegistration(void)
         uint8_t pbbrServiceId;
 
         SuccessOrExit(error = Get<BackboneRouter::Leader>().GetServiceId(pbbrServiceId));
-        SuccessOrExit(error = mle.GetServiceAloc(pbbrServiceId, messageInfo.GetPeerAddr()));
+        mle.GetServiceAloc(pbbrServiceId, messageInfo.GetPeerAddr());
     }
     else
     {