[tlvs] use Tlv::Info for reading TLV values (#12322)

This change moves the TLV value reading logic from static methods in
the `Tlv` class to member methods of the nested `Tlv::Info` class.

The new methods `Tlv::Info::ReadValue()`, `Tlv::Info::ReadStringValue()`,
`Tlv::Info::ReadUintValue()`, and the templated `Tlv::Info::Read<T>()`
operate on an existing `Tlv::Info` object that has already parsed a
TLV from a message.

This improves the API design by having the read operations use the
pre-parsed and validated state within a `Tlv::Info` instance. It
avoids the need to pass the TLV offset to read functions and
eliminates redundant re-parsing of the TLV header on each read,
making the code cleaner and more efficient.

The previous static methods `Tlv::Read<T>()`, `Tlv::ReadStringTlv()`,
and `Tlv::ReadUintTlv()` are removed, and all call sites are updated
to the new pattern.

src/core/thread/mle_ftd.cpp

@@ -2731,14 +2731,13 @@ void Mle::HandleDiscoveryRequest(RxInfo &aRxInfo)
         switch (tlvInfo.GetType())
         {
         case MeshCoP::Tlv::kDiscoveryRequest:
-            SuccessOrExit(error = Tlv::Read<MeshCoP::DiscoveryRequestTlv>(aRxInfo.mMessage, offsetRange.GetOffset(),
-                                                                          discoveryRequestTlvValue));
+            SuccessOrExit(error =
+                              tlvInfo.Read<MeshCoP::DiscoveryRequestTlv>(aRxInfo.mMessage, discoveryRequestTlvValue));
             parsedDiscoveryRequestTlv = true;
             break;
 
         case MeshCoP::Tlv::kExtendedPanId:
-            SuccessOrExit(
-                error = Tlv::Read<MeshCoP::ExtendedPanIdTlv>(aRxInfo.mMessage, offsetRange.GetOffset(), extPanId));
+            SuccessOrExit(error = tlvInfo.Read<MeshCoP::ExtendedPanIdTlv>(aRxInfo.mMessage, extPanId));
             VerifyOrExit(Get<MeshCoP::ExtendedPanIdManager>().GetExtPanId() != extPanId, error = kErrorDrop);
 
             break;