[nexus] simplify node lookup using LinkedList matching methods (#12849)

This commit updates the address-based node lookup methods in `Core`
to use the `FindMatching()` and `ContainsMatching()` methods provided
by the `LinkedList` class. This replaces manual `for` loops with
cleaner, built-in list operations.

To facilitate this, a new `AddressNetif` enum and a `Matches()` method
are added to the `Node` class. The `Matches()` method accepts an
`Ip6::Address` and an `AddressNetif` indicator, allowing it to check
if the node has the specified address on its Thread interface, its
Infrastructure interface, or any.

Additionally, a `const` overload for the `Get()` template method is
added to the `Node` class to ensure proper const-correctness.

tests/nexus/platform/nexus_node.cpp

@@ -229,5 +229,27 @@ const Ip6::Address &Node::FindGlobalAddress(void)
     return *matchedAddress;
 }
 
+bool Node::Matches(const Ip6::Address &aAddress, AddressNetif aNetif) const
+{
+    bool matches = false;
+
+    switch (aNetif)
+    {
+    case kThreadNetifAddress:
+        matches = Get<ThreadNetif>().HasUnicastAddress(aAddress);
+        break;
+
+    case kInfraNetifAddress:
+        matches = mInfraIf.HasAddress(aAddress);
+        break;
+
+    case kAnyNetifAddress:
+        matches = Get<ThreadNetif>().HasUnicastAddress(aAddress) || mInfraIf.HasAddress(aAddress);
+        break;
+    }
+
+    return matches;
+}
+
 } // namespace Nexus
 } // namespace ot