fix: Conftest can now successfully load files using a file URL (e.g., file:///C:/path/to/data.yaml) on windows (#999)

* fix:
    Conftest encounters errors on Windows when loading file paths that include drive letters (e.g., `C:/path/to/data.yaml`).
    Even when using a file URL (e.g., `file:///C:/path/to/data.yaml`), we still face issues.
    With these code changes, Conftest can now successfully load files using a file URL (e.g., `file:///C:/path/to/data.yaml`).
    We opted for file URLs instead of paths with drive letters (e.g., `C:/path/to/data.yaml`) because OPA does not support file paths with drive letters. For more details, see [this issue comment](open-policy-agent/opa#6922 (comment)).

    Resolves: #979

Signed-off-by: Punith C K <pck@veracode.com>

* fix:
Removing WithProcessAnnotation(true) which is not needed for loading data files

Signed-off-by: Punith C K <punithck@itsupports-Laptop.local>

* fix: Conftest can now successfully load files using a file URL (e.g., file:///C:/path/to/data.yaml) on windows
Removing duplicate code

Signed-off-by: Punith C K <pck@veracode.com>

---------

Signed-off-by: Punith C K <punithck@itsupports-Laptop.local>
Signed-off-by: Punith C K <pck@veracode.com>
Co-authored-by: Punith C K <punithck@itsupports-Laptop.local>

Author: pckvcode

policy/engine.go

@@ -125,20 +125,14 @@ func LoadWithData(policyPaths []string, dataPaths []string, opts CompilerOptions
 			return nil, fmt.Errorf("loading policies: %w", err)
 		}
 	}
-
-	// FilteredPaths will recursively find all file paths that contain a valid document
-	// extension from the given list of data paths.
-	allDocumentPaths, err := loader.FilteredPaths(dataPaths, func(_ string, info os.FileInfo, _ int) bool {
+	filter := func(_ string, info os.FileInfo, _ int) bool {
 		if info.IsDir() {
 			return false
 		}
 		return !contains([]string{".yaml", ".yml", ".json"}, filepath.Ext(info.Name()))
-	})
-	if err != nil {
-		return nil, fmt.Errorf("filter data paths: %w", err)
 	}
 
-	documents, err := loader.NewFileLoader().All(allDocumentPaths)
+	documents, err := loader.NewFileLoader().Filtered(dataPaths, filter)
 	if err != nil {
 		return nil, fmt.Errorf("load documents: %w", err)
 	}
@@ -147,6 +141,12 @@ func LoadWithData(policyPaths []string, dataPaths []string, opts CompilerOptions
 		return nil, fmt.Errorf("get documents store: %w", err)
 	}
 
+	// FilteredPaths will recursively find all file paths that contain a valid document
+	// extension from the given list of data paths.
+	allDocumentPaths, err := loader.FilteredPaths(dataPaths, filter)
+	if err != nil {
+		return nil, fmt.Errorf("filter data paths: %w", err)
+	}
 	documentContents := make(map[string]string)
 	for _, documentPath := range allDocumentPaths {
 		contents, err := os.ReadFile(documentPath)