Fix Abs path validation on Windows (#124084)

* Windows: Consider slash-prefixed paths as absolute

filepath.IsAbs does not consider "/" or "\" as absolute paths, even
though files can be addressed as such. [1][2]

Currently, there are some unit tests that are failing on Windows due to
this reason.

[1] https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats#traditional-dos-paths
[2] https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file#fully-qualified-vs-relative-paths

* Add test to verify IsAbs for windows

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

* Fix abs path validation on windows

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

* Skipp path clean check for podLogDir on windows

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

* Implement IsPathClean to validate path

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

* Add warn comment for IsAbs

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

---------

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>
Co-authored-by: Claudiu Belu <cbelu@cloudbasesolutions.com>

pkg/util/filesystem/util.go

@@ -0,0 +1,27 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package filesystem
+
+import (
+	"path/filepath"
+)
+
+// IsPathClean will replace slashes to Separator (which is OS-specific).
+// This will make sure that all slashes are the same before comparing.
+func IsPathClean(path string) bool {
+	return filepath.ToSlash(filepath.Clean(path)) == filepath.ToSlash(path)
+}