scripted-diff: Rename m_is_loaded -> m_load_tried

m_is_loaded/IsLoaded() doesn't actually indicate whether or not the
mempool was successfully, loaded, but rather if a load has been
attempted and did not result in a catastrophic ShutdownRequested.

-BEGIN VERIFY SCRIPT-
find_regex="\bm_is_loaded\b" \
    && git grep -l -E "$find_regex" \
        | xargs sed -i -E "s@$find_regex@m_load_tried@g"

find_regex="\bIsLoaded\b" \
    && git grep -l -E "$find_regex" \
        | xargs sed -i -E "s@$find_regex@GetLoadTried@g"

find_regex="\bSetIsLoaded\b" \
    && git grep -l -E "$find_regex" \
        | xargs sed -i -E "s@$find_regex@SetLoadTried@g"
-END VERIFY SCRIPT-

src/validation.cpp

@@ -3869,7 +3869,7 @@ void CChainState::LoadMempool(const ArgsManager& args)
     if (args.GetBoolArg("-persistmempool", DEFAULT_PERSIST_MEMPOOL)) {
         ::LoadMempool(*m_mempool, *this);
     }
-    m_mempool->SetIsLoaded(!ShutdownRequested());
+    m_mempool->SetLoadTried(!ShutdownRequested());
 }
 
 bool CChainState::LoadChainTip()