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_windows_test.go

@@ -89,3 +89,12 @@ func TestPendingUnixDomainSocket(t *testing.T) {
 	wg.Wait()
 	unixln.Close()
 }
+
+func TestAbsWithSlash(t *testing.T) {
+	// On Windows, filepath.IsAbs will not return True for paths prefixed with a slash
+	assert.True(t, IsAbs("/test"))
+	assert.True(t, IsAbs("\\test"))
+
+	assert.False(t, IsAbs("./local"))
+	assert.False(t, IsAbs("local"))
+}