Merge #19174: refactor: replace CConnman pointers by references in net_processing.cpp

0c8461a88e refactor: replace CConnman pointers by references in net_processing.cpp (Sebastian Falbesoner)

Pull request description:

  This is a follow-up to the recently merged PR https://github.com/bitcoin/bitcoin/pull/19053, replacing ~~two more types of~~ one more type of pointer (CConnman) by references to increase the code quality -- pointers should either check for `nullptr` or be replaced by references, and the latter strategy seems to be more reasonable.

  Again, to keep the review burden managable, the changes are kept simple,
  * only tackling `CConnman*` ~~and `BanMan*`~~ pointers
  * only within the net_processing module, i.e. no changes that would need adaption in other modules
  * keeping the names of the variables as they are

ACKs for top commit:
  jnewbery:
    utACK 0c8461a88e
  MarcoFalke:
    ACK 0c8461a88e 🕧

Tree-SHA512: 79dc05144bcfb5e0bbc62180285aadcc6199f044fa3016c0f54f7b7f45037415260970037bd63b18fafefb8aef448549dae14b780bafb540fa2373f493a17f71

src/test/fuzz/process_message.cpp

@@ -38,7 +38,7 @@ void ProcessMessage(
     const CChainParams& chainparams,
     ChainstateManager& chainman,
     CTxMemPool& mempool,
-    CConnman* connman,
+    CConnman& connman,
     BanMan* banman,
     const std::atomic<bool>& interruptMsgProc);
 
@@ -89,7 +89,7 @@ void test_one_input(const std::vector<uint8_t>& buffer)
     try {
         ProcessMessage(p2p_node, random_message_type, random_bytes_data_stream, GetTime<std::chrono::microseconds>(),
             Params(), *g_setup->m_node.chainman, *g_setup->m_node.mempool,
-            g_setup->m_node.connman.get(), g_setup->m_node.banman.get(),
+            *g_setup->m_node.connman, g_setup->m_node.banman.get(),
             std::atomic<bool>{false});
     } catch (const std::ios_base::failure&) {
     }