Merge #5883: refactor: use atomic to avoid blocking chainlocks cs on …

…each call to cleanup

75d81fd refactor: use atomic to avoid blocking chainlocks cs on each call to cleanup (pasta)

Pull request description:

  ## Issue being fixed or feature implemented
  Avoid needing to lock CS on each call to cleanup. Cleanup only gets called once every 5 seconds it seems; but maybe that'll change in the future.

  ## What was done?
  Make `lastCleanupTime` atomic instead of CS guarded

  ## How Has This Been Tested?
  Building

  ## Breaking Changes
  None

  ## Checklist:
    _Go over all the following points, and put an `x` in all the boxes that apply._
  - [x] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

Top commit has no ACKs.

Tree-SHA512: 587dbfbecce430c25b4d572b2e158fcda86aced3db976c16166c0cabcf960f46d300739bbf54644def30769347cc88ac14c58d71dd78d848f7d8af562cd12bc6

src/llmq/chainlocks.cpp

@@ -617,11 +617,8 @@ void CChainLocksHandler::Cleanup()
         return;
     }
 
-    {
-        LOCK(cs);
-        if (GetTimeMillis() - lastCleanupTime < CLEANUP_INTERVAL) {
-            return;
-        }
+    if (GetTimeMillis() - lastCleanupTime < CLEANUP_INTERVAL) {
+        return;
     }
 
     // need mempool.cs due to GetTransaction calls

src/llmq/chainlocks.h

@@ -82,7 +82,7 @@ class CChainLocksHandler : public CRecoveredSigsListener
 
     std::map<uint256, int64_t> seenChainLocks GUARDED_BY(cs);
 
-    int64_t lastCleanupTime GUARDED_BY(cs) {0};
+    std::atomic<int64_t> lastCleanupTime{0};
 
 public:
     explicit CChainLocksHandler(CChainState& chainstate, CConnman& _connman, CMasternodeSync& mn_sync, CQuorumManager& _qman,