I hope you still have a chance to get your review in this cycle; no reviewer had been assigned since January.
It compiles, builds, and runs make check-world cleanly.
Preferably apply the patches in the order below (or I can consolidate them into a single patch if you wish)
64bitGUCs_INT64
XID_FMT
ClogPageNumber
FixMergeConflicts_26Mar2021