I think that if a reorg fails due to an error while disconnecting blocks, the node should shut down.

My thought is that if we are trying to switch to a more work chain and something goes wrong before we can even try to validate that more-work chain, then we have a problem that is not related to the chain we're trying to switch to but instead related to our own hardware or software; shutting down and having the user deal with the issue is better than continuing on, when we know there's a more work chain that we're unable to try validating.

This has recently come up on testnet, where unpatched nodes are unable to reorg from the invalid chain containing the duplicate-input-in-a-transaction block, but rather than crash or shutdown they are continuing on the invalid chain, with messages like this in the debug log:

```
ERROR: DisconnectTip(): DisconnectBlock 00000000210004840364b52bc5e455d888f164e4264a4fec06a514b67e9d5722 failed
```
FindFilesToPruneManual(setFilesToPrune, nManualPruneHeight);
            } else {
                FindFilesToPrune(setFilesToPrune, chainparams.PruneAfterHeight());
                fCheckForPruning = false;
            }
            if (!setFilesToPrune.empty()) {
                fFlushForPrune = true;
                if (!fHavePruned) {
                    pblocktree->WriteFlag("prunedblockfiles", true);
                    fHavePruned = true;
                }
            }
        }
        int64_t nNow = GetTimeMicros();
        
        if (nLastWrite == 0) {
            nLastWrite = nNow;
        }
        if (nLastFlush == 0) {
            nLastFlush = nNow;
        }
        int64_t nMempoolSizeMax = gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
        int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
        int64_t nTotalSpace = nCoinCacheUsage + std::max<int64_t>(nMempoolSizeMax - nMempoolUsage, 0);
        
        bool fCacheLarge = mode == FlushStateMode::PERIODIC && cacheSize > std::max((9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE * 1024 * 1024);
        
        bool fCacheCritical = mode == FlushStateMode::IF_NEEDED && cacheSize > nTotalSpace;
        
        bool fPeriodicWrite = mode == FlushStateMode::PERIODIC && nNow > nLastWrite + (int64_t)DATABASE_WRITE_INTERVAL * 1000000;