[net/refactor] Extract m_addr_known logic from initializer list

Summary:
Partial backport (6/19) of core [[bitcoin/bitcoin#19316 | PR19316]]:
bitcoin/bitcoin@af59feb

Depends on D8715.

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D8716

src/net.cpp

@@ -2996,16 +2996,14 @@ CNode::CNode(NodeId idIn, ServiceFlags nLocalServicesIn,
       // Don't relay addr messages to peers that we connect to as
       // block-relay-only peers (to prevent adversaries from inferring these
       // links from addr traffic).
-      m_addr_known{conn_type_in == ConnectionType::BLOCK_RELAY
-                       ? nullptr
-                       : std::make_unique<CRollingBloomFilter>(5000, 0.001)},
       id(idIn), nLocalHostNonce(nLocalHostNonceIn),
       nLocalServices(nLocalServicesIn), nMyStartingHeight(nMyStartingHeightIn) {
     hSocket = hSocketIn;
     addrName = addrNameIn == "" ? addr.ToStringIPPort() : addrNameIn;
     hashContinue = BlockHash();
     if (conn_type_in != ConnectionType::BLOCK_RELAY) {
         m_tx_relay = std::make_unique<TxRelay>();
+        m_addr_known = std::make_unique<CRollingBloomFilter>(5000, 0.001);
     }
 
     for (const std::string &msg : getAllNetMessageTypes()) {

src/net.h

@@ -872,7 +872,7 @@ class CNode {
 
     // flood relay
     std::vector<CAddress> vAddrToSend;
-    const std::unique_ptr<CRollingBloomFilter> m_addr_known;
+    std::unique_ptr<CRollingBloomFilter> m_addr_known = nullptr;
     bool fGetAddr{false};
     std::chrono::microseconds m_next_addr_send GUARDED_BY(cs_sendProcessing){0};
     std::chrono::microseconds