Fix more holes with SLRU code in need of int64 for segment numbers

This is a continuation of c9e2457390, containing changes included into
the proposed patch that have been missed in the actual commit.  I have
managed to miss these diffs while doing a rebase of the original patch.

Thanks to Noah Misch, Peter Eisentraut and Alexander Korotkov for the
pokes.

Discussion: https://postgr.es/m/92fe572d-638e-4162-aef6-1c42a2936f25@eisentraut.org
Discussion: https://postgr.es/m/20240810175055.cd.nmisch@google.com
Backpatch-through: 17

src/backend/access/transam/multixact.c

@@ -120,7 +120,7 @@ MultiXactIdToOffsetEntry(MultiXactId multi)
 	return multi % MULTIXACT_OFFSETS_PER_PAGE;
 }
 
-static inline int
+static inline int64
 MultiXactIdToOffsetSegment(MultiXactId multi)
 {
 	return MultiXactIdToOffsetPage(multi) / SLRU_PAGES_PER_SEGMENT;
@@ -174,7 +174,7 @@ MXOffsetToMemberPage(MultiXactOffset offset)
 	return offset / MULTIXACT_MEMBERS_PER_PAGE;
 }
 
-static inline int
+static inline int64
 MXOffsetToMemberSegment(MultiXactOffset offset)
 {
 	return MXOffsetToMemberPage(offset) / SLRU_PAGES_PER_SEGMENT;
@@ -3039,10 +3039,10 @@ SlruScanDirCbFindEarliest(SlruCtl ctl, char *filename, int64 segpage, void *data
 static void
 PerformMembersTruncation(MultiXactOffset oldestOffset, MultiXactOffset newOldestOffset)
 {
-	const int	maxsegment = MXOffsetToMemberSegment(MaxMultiXactOffset);
-	int			startsegment = MXOffsetToMemberSegment(oldestOffset);
-	int			endsegment = MXOffsetToMemberSegment(newOldestOffset);
-	int			segment = startsegment;
+	const int64 maxsegment = MXOffsetToMemberSegment(MaxMultiXactOffset);
+	int64		startsegment = MXOffsetToMemberSegment(oldestOffset);
+	int64		endsegment = MXOffsetToMemberSegment(newOldestOffset);
+	int64		segment = startsegment;
 
 	/*
 	 * Delete all the segments but the last one. The last segment can still

src/backend/access/transam/slru.c

@@ -1532,7 +1532,7 @@ restart:
 	did_write = false;
 	for (int slotno = 0; slotno < shared->num_slots; slotno++)
 	{
-		int			pagesegno;
+		int64		pagesegno;
 		int			curbank = SlotGetBankNumber(slotno);
 
 		/*