Merge bitcoin/bitcoin#22696: p2p: log addrman consistency checks

4844b74 p2p: log addrman consistency checks (Jon Atack)

Pull request description:

  This mini-patch picks up #22479 to log addrman consistency checks in the `BCLOG::ADDRMAN` category when they are enabled with the `-checkaddrman=<n>` configuration option for values of n greater than 0.

  ```
  $ ./src/bitcoind -signet -checkaddrman=20 -debug=addrman
  ...
  2021-08-13T11:14:45Z Addrman checks started: new 3352, tried 89, total 3441
  2021-08-13T11:14:45Z Addrman checks completed successfully
  ```

  This allows people to
  - verify the checks are running
  - see when and how often they are being performed
  - see the number of new/tried/total addrman entries per check
  - see the start/end of the checks

  Thanks to John Newbery for ideas to improve this logging.

ACKs for top commit:
  jnewbery:
    Code review ACK 4844b74
  Zero-1729:
    tACK 4844b74
  theStack:
    Concept and code-review ACK 4844b74 ♟️

Tree-SHA512: 10b51c480d52a753ea8a59dbdd1e2c4f49067e7f4afe59d58426a8fb438f52447fe3a6090fa52132bc382d876927fa338b229c906d85668086f7f8f5bd8ed38a

Author: fanquake

src/addrman.cpp

@@ -439,6 +439,8 @@ int CAddrMan::Check_() const
     if (m_consistency_check_ratio == 0) return 0;
     if (insecure_rand.randrange(m_consistency_check_ratio) >= 1) return 0;
 
+    LogPrint(BCLog::ADDRMAN, "Addrman checks started: new %i, tried %i, total %u\n", nNew, nTried, vRandom.size());
+
     std::unordered_set<int> setTried;
     std::unordered_map<int, int> mapNew;
 
@@ -517,6 +519,7 @@ int CAddrMan::Check_() const
     if (nKey.IsNull())
         return -16;
 
+    LogPrint(BCLog::ADDRMAN, "Addrman checks completed successfully\n");
     return 0;
 }