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/kubelet/kubeletconfig/configfiles/configfiles.go

@@ -100,7 +100,7 @@ func resolveRelativePaths(paths []*string, root string) {
 	for _, path := range paths {
 		// leave empty paths alone, "no path" is a valid input
 		// do not attempt to resolve paths that are already absolute
-		if len(*path) > 0 && !filepath.IsAbs(*path) {
+		if len(*path) > 0 && !utilfs.IsAbs(*path) {
 			*path = filepath.Join(root, *path)
 		}
 	}