Avoid overflow in MaybeRemoveOldWalSummaries().

This commit limits the maximum value of wal_summary_keep_time to
INT_MAX / SECS_PER_MINUTE to avoid overflow when it is converted to
seconds.  In passing, use the HOURS_PER_DAY, MINS_PER_HOUR, and
SECS_PER_MINUTE macros in the code for this GUC instead of hard-
coding those values.

Discussion: https://postgr.es/m/20240314210010.GA3056455%40nathanxps13

Author: nathan-bossart

src/backend/postmaster/walsummarizer.c

@@ -140,7 +140,7 @@ static XLogRecPtr redo_pointer_at_last_summary_removal = InvalidXLogRecPtr;
  * GUC parameters
  */
 bool		summarize_wal = false;
-int			wal_summary_keep_time = 10 * 24 * 60;
+int			wal_summary_keep_time = 10 * HOURS_PER_DAY * MINS_PER_HOUR;
 
 static void WalSummarizerShutdown(int code, Datum arg);
 static XLogRecPtr GetLatestLSN(TimeLineID *tli);
@@ -1480,7 +1480,7 @@ MaybeRemoveOldWalSummaries(void)
 	 * Files should only be removed if the last modification time precedes the
 	 * cutoff time we compute here.
 	 */
-	cutoff_time = time(NULL) - 60 * wal_summary_keep_time;
+	cutoff_time = time(NULL) - wal_summary_keep_time * SECS_PER_MINUTE;
 
 	/* Get all the summaries that currently exist. */
 	wslist = GetWalSummaries(0, InvalidXLogRecPtr, InvalidXLogRecPtr);

src/backend/utils/misc/guc_tables.c

@@ -3293,9 +3293,9 @@ struct config_int ConfigureNamesInt[] =
 			GUC_UNIT_MIN,
 		},
 		&wal_summary_keep_time,
-		10 * 24 * 60,			/* 10 days */
+		10 * HOURS_PER_DAY * MINS_PER_HOUR, /* 10 days */
 		0,
-		INT_MAX,
+		INT_MAX / SECS_PER_MINUTE,
 		NULL, NULL, NULL
 	},