Prevent CRLF conversion of inputs in json_parser test module

Do this by opening the file in PG_BINARY_R mode. This prevents us from
getting wrong byte count from stat().

Per complaint from Andres Freund

Discussion: https://postgr.es/m/20240707052030.r77hbdkid3mwksop@awork3.anarazel.de

Backpatch to rlease 17 where this code was introduced

Author: adunstan

src/test/modules/test_json_parser/test_json_parser_incremental.c

@@ -124,7 +124,7 @@ main(int argc, char **argv)
 	makeJsonLexContextIncremental(&lex, PG_UTF8, need_strings);
 	initStringInfo(&json);
 
-	if ((json_file = fopen(testfile, "r")) == NULL)
+	if ((json_file = fopen(testfile, PG_BINARY_R)) == NULL)
 		pg_fatal("error opening input: %m");
 
 	if (fstat(fileno(json_file), &statbuf) != 0)

src/test/modules/test_json_parser/test_json_parser_perf.c

@@ -55,7 +55,7 @@ main(int argc, char **argv)
 
 	sscanf(argv[1], "%d", &iter);
 
-	if ((json_file = fopen(argv[2], "r")) == NULL)
+	if ((json_file = fopen(argv[2], PG_BINARY_R)) == NULL)
 		pg_fatal("Could not open input file '%s': %m", argv[2]);
 
 	while ((n_read = fread(buff, 1, 6000, json_file)) > 0)