Merge bitcoin/bitcoin#27015: p2p: 26847 fixups (AddrMan totals)

dc70c1e addrman: Use std::nullopt instead of {} (Martin Zumsande)
59cc66a test: Remove AddrMan unit test that fails consistency checks (Martin Zumsande)

Pull request description:

  Two fixups for #26847:
  * Now that `AddrMan::Size()` performs internal consistency tests (it didn't before), we can't call it in the `load_addrman_corrupted` unit tests, where we deal with an artificially corrupted `AddrMan`. This would fail the test when using `-checkaddrman=1` (leading to spurious CI fails). Therefore remove the tests assertion, which is not particularly helpful anyway (in production we abort init when peers.dat is corrupted instead of querying AddrMan in its corrupted state).
   (See bitcoin/bitcoin#26847 (comment))
  * Use `std::nullopt` instead of `{}` for default args (suggested in bitcoin/bitcoin#26847 (comment))

ACKs for top commit:
  MarcoFalke:
    lgtm ACK dc70c1e

Tree-SHA512: dd8a988e23d71a66d3dd30560bb653c9ad17db6915abfa5f722818b0ab18921051ec9223bfbc75d967df8bcd204dfe473d680bf68e8a8e4e4998fbb91dc973c5

Author: fanquake

src/addrman.h

@@ -106,7 +106,7 @@ class AddrMan
     * @param[in] in_new           Select addresses only from one table (true = new, false = tried, nullopt = both)
     * @return                     Number of unique addresses that match specified options.
     */
-    size_t Size(std::optional<Network> net = {}, std::optional<bool> in_new = {}) const;
+    size_t Size(std::optional<Network> net = std::nullopt, std::optional<bool> in_new = std::nullopt) const;
 
     /**
      * Attempt to add one or more addresses to addrman's new table.

src/test/addrman_tests.cpp

@@ -947,8 +947,6 @@ BOOST_AUTO_TEST_CASE(load_addrman_corrupted)
     } catch (const std::exception&) {
         exceptionThrown = true;
     }
-    // Even though de-serialization failed addrman is not left in a clean state.
-    BOOST_CHECK(addrman1.Size() == 1);
     BOOST_CHECK(exceptionThrown);
 
     // Test that ReadFromStream fails if peers.dat is corrupt