Add ledger.history.mismatch insight statistic
Make sure we update mTNByID when we replace the root
Improve parallelization of getRippleLines
Speed-up path element operations & comparisons
Use std::map to optimize lookup performance
[FOLD] address Vinnie's comment
[FOLD] Improve linecache performance:
Based on an idea by David, use a proxy object to calculate the hash
value of an Account outside the lock and improve the performance of
comparison operations during inserts and lookups. Also use emplace
instead of a find/insert pair of calls.