feat(dcl): move the OPC UA client to OPC Foundation SDK 2.0.1 (#125)

OPCFoundation.NetStandard.Opc.Ua.Client and the test-only .Server move
1.5.378.182 -> 2.0.1, the version OtOpcUa master runs (lmxopcua#782; #799
and #801 closed). Transitive Core/Core.Types/Types/Configuration/
Security.Certificates resolve to 2.0.1.

API breaks fixed in the DCL adapter:
- Built-in types are immutable structs (Variant, DataValue, NodeId,
  LocalizedText, StatusCode, ArrayOf<T>). New OpcUaValueBoundary restores
  the SDK 1.5 CLR shapes for every read, subscription and alarm-event
  value (byte[], UTC DateTime with no-timestamp = MinValue, Guid,
  detached arrays) and builds write variants with SDK 1.5's
  new Variant(object) semantics (byte[] = ByteString scalar).
- StatusCodes members are no longer constants: switches/patterns over
  them (verify-outcome mapping, connection-level classification,
  BadResourceUnavailable) match by value.
- CertificateIdentifier no longer caches a certificate and the
  CertificateValidator/CertificateValidation event is gone: the
  configuration's CertificateManager owns trust lists and the loaded
  application certificate and is disposed with the session; auto-accept
  and the verify probe's capture-and-reject use AcceptError.
- new UserIdentity(X509Certificate2) is gone: X509 user identities use
  X509IdentityTokenHandler with an on-demand PFX provider (still fails
  fast on a missing file/key).
- DefaultSessionFactory takes the telemetry context; collections are
  ArrayOf<T>; EventFilter select clauses and ContentFilter operands are
  built immutably.

UserName identity (lmxopcua#880): SDK 2's default handler sends a
password over 64 bytes - every 65-character OtOpcUa API key - as an
RsaEncryptedSecret that SDK 1.5 servers reject with BadIdentityTokenInvalid
and SDK 2 servers accept only within a 5-minute clock window (#873). The
DCL now always uses LegacyRsaUserNameIdentityTokenHandler (ported from
OtOpcUa be28aa44), i.e. exactly what it sent on SDK 1.5, so it logs in to
both server generations during a mixed rollout.

Tests: the in-process secured test server is ported to SDK 2 and can
admit an API key; new tests cover the handler (mutation-checked: 5 of 7
fail with the SDK default handler), the value boundary, and a 65-char key
end to end over None/Sign/SignAndEncrypt with a wrong key reaching the
key check (BadIdentityTokenRejected).

Claude-Session: https://claude.ai/code/session_01GT67ACmpMR7b9LGRPLijMi

tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/Adapters/OpcUaNodeReferenceTests.cs

@@ -40,7 +40,7 @@ public class OpcUaNodeReferenceTests
         var nodeId = OpcUaNodeReference.Resolve("ns=2;s=pymodbus/plc/HR200", V3Table());
 
         Assert.Equal(2, nodeId.NamespaceIndex);
-        Assert.Equal("pymodbus/plc/HR200", nodeId.Identifier);
+        Assert.Equal("pymodbus/plc/HR200", nodeId.IdentifierAsString);
     }
 
     /// <summary>Verifies that the namespace URI form resolves to the server's live namespace index.</summary>
@@ -50,7 +50,7 @@ public class OpcUaNodeReferenceTests
         var nodeId = OpcUaNodeReference.Resolve($"nsu={RawUri};s=pymodbus/plc/HR200", V3Table());
 
         Assert.Equal(2, nodeId.NamespaceIndex);
-        Assert.Equal("pymodbus/plc/HR200", nodeId.Identifier);
+        Assert.Equal("pymodbus/plc/HR200", nodeId.IdentifierAsString);
     }
 
     /// <summary>Verifies that the namespace URI form tracks the index across servers with different namespace tables.</summary>
@@ -159,7 +159,7 @@ public class OpcUaNodeReferenceTests
         var resolved = OpcUaNodeReference.Resolve(durable, table);
 
         Assert.Equal(3, resolved.NamespaceIndex);
-        Assert.Equal("Area/Line/Equip/Speed", resolved.Identifier);
+        Assert.Equal("Area/Line/Equip/Speed", resolved.IdentifierAsString);
     }
 
     /// <summary>Verifies that a URI missing from the namespace table falls back instead of throwing.</summary>