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/init.cpp

@@ -249,7 +249,7 @@ void Shutdown(NodeContext& node)
     node.addrman.reset();
     node.netgroupman.reset();
 
-    if (node.mempool && node.mempool->IsLoaded() && ShouldPersistMempool(*node.args)) {
+    if (node.mempool && node.mempool->GetLoadTried() && ShouldPersistMempool(*node.args)) {
         DumpMempool(*node.mempool, MempoolPath(*node.args));
     }