python tests: forward-slash pg_waldump --path archive arguments on Windows

The pg_waldump basic test feeds --path the pgdata directory and, for the
archive scenarios, the pg_wal.tar / pg_wal.tar.gz paths built with
os.path.join (backslashes on Windows).  pg_waldump splits the path on "/",
so the backslash form made it fail to open the archive.  Normalize the
scenario path to forward slashes, matching the other WAL path fixes.

Author: adunstan

src/bin/pg_waldump/pyt/test_001_basic.py

@@ -428,7 +428,8 @@ def test_pg_waldump_basic(pg_bin, create_pg, pg_config, tempdir_short):
     ]
 
     for scenario in scenarios:
-        path = scenario["path"]
+        # pg_waldump splits the path on "/", so feed it forward slashes.
+        path = scenario["path"].replace("\\", "/")
 
         if scenario["is_archive"] and (not tar):
             # skip "tar command is not available"