mount: report . and .. from windows directories (#10556)

* mount: report . and .. from windows directories

WinFsp strips the dot entries for the root itself and expects every other
directory to report them, the way a real NTFS enumeration does: its
dirctl test asserts a subdirectory's first two entries are "." and ".."
and that a hundred files enumerate as 102 entries. Dropping them
unconditionally is what fails querydir_test.

The Go test that guarded the old behaviour went with it: os.File.Readdir
filters dot entries itself, so it could never have observed either way.

* mount: give the windows dot entries their directory type

The readdir fills an attribute block only for real children, so "." and
".." arrived with a zeroed one and were reported with mode 0. Windows
refuses to enumerate a directory whose first entry is not marked as a
directory, which is the assertion querydir_test fails on with
STATUS_OBJECT_NAME_NOT_FOUND.

They now carry the type the readdir already knew. The explorer walk also
names any unexpected entry rather than only counting, so a dot entry
leaking through reads differently from a missing file.

test/winfsp-conformance/known_failures.txt

@@ -73,10 +73,9 @@ setfileinfo_test
 
 # Directory enumeration
 # ---------------------
-# Marker-based resumption and the buffer-overflow path, neither of which the
-# hand-written suite reaches.
-querydir_test
-querydir_buffer_overflow_test
+# querydir_namelen only: checkName caps at 255 bytes while WinFsp counts 255
+# characters. The other two are expected to pass now that "." and ".." are
+# reported for non-root directories, which is what WinFsp enumerates.
 querydir_namelen_test
 
 # Name length

test/winfsp/semantics_test.go

@@ -270,35 +270,6 @@ func TestAwkwardNames(t *testing.T) {
 	}
 }
 
-// Windows enumerates a directory without "." and "..", and shows whatever the
-// filesystem reports, so they must not reach it. os.ReadDir filters them, so
-// this reads the handle the way Windows tooling does.
-func TestNoDotEntriesInListing(t *testing.T) {
-	dir := testRoot(t)
-	for i := 0; i < 3; i++ {
-		if err := os.WriteFile(filepath.Join(dir, fmt.Sprintf("f%d", i)), []byte("x"), 0644); err != nil {
-			t.Fatalf("write: %v", err)
-		}
-	}
-	f, err := os.Open(dir)
-	if err != nil {
-		t.Fatalf("open dir: %v", err)
-	}
-	defer f.Close()
-	names, err := f.Readdirnames(-1)
-	if err != nil {
-		t.Fatalf("readdirnames: %v", err)
-	}
-	for _, name := range names {
-		if name == "." || name == ".." {
-			t.Errorf("listing includes %q", name)
-		}
-	}
-	if len(names) != 3 {
-		t.Fatalf("listing has %d entries (%v), want 3", len(names), names)
-	}
-}
-
 func TestDeepDirectoryNesting(t *testing.T) {
 	dir := testRoot(t)
 	deep := dir