Add fs.ResolvePath to resolve symbolic links (#275)

* Add `fs.ResolvePath` to resolve symbolic links

`filepath.EvalSymlinks` does not work well on Windows, and can enter
infinite loops in certain situations and error out.
Use Win32 API GetFinalPathNameByHandle to handle path resolution.

Implementation based off on: https://github.com/containerd/containerd/pull/5411

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* PR: types, documentation

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* remove unneded constant groups

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

* Attempt normalized path first

Update logic to try querying for normalized path initially, then use
opened path if access is denied.

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

---------

Signed-off-by: Hamza El-Saawy <hamzaelsaawy@microsoft.com>

internal/fs/fs_test.go

@@ -0,0 +1,42 @@
+//go:build windows
+
+package fs
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"golang.org/x/sys/windows"
+)
+
+func Test_GetFinalPathNameByHandle(t *testing.T) {
+	d := t.TempDir()
+	// open f via a relative path
+	name := t.Name() + ".txt"
+	fullPath := filepath.Join(d, name)
+
+	w, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("could not get working directory: %v", err)
+	}
+	if err := os.Chdir(d); err != nil {
+		t.Fatalf("could not chdir to %s: %v", d, err)
+	}
+	defer os.Chdir(w) //nolint:errcheck
+
+	f, err := os.Create(name)
+	if err != nil {
+		t.Fatalf("could not open %s: %v", fullPath, err)
+	}
+	defer f.Close()
+
+	path, err := GetFinalPathNameByHandle(windows.Handle(f.Fd()), GetFinalPathDefaultFlag)
+	if err != nil {
+		t.Fatalf("could not get final path for %s: %v", fullPath, err)
+	}
+	if strings.EqualFold(fullPath, path) {
+		t.Fatalf("expected %s, got %s", fullPath, path)
+	}
+}