Add a debug message to inform the Filter property value read.

See more in https://mail.openjdk.org/pipermail/security-dev/2024-October/041800.html

Co-authored-by: Martin Balao Alonso <[email protected]>
Co-authored-by: Francisco Ferrari Bihurriet <[email protected]>

Author: martinuy

src/java.base/share/classes/sun/security/jca/ProvidersFilter.java

@@ -671,6 +671,12 @@ public String toString() {
     static {
         Filter tmpFilter = null;
         String fStr = SecurityProperties.getOverridableProperty(FILTER_PROP);
+        if (debug != null) {
+            debug.println("Filter property value read at this point:");
+            for (StackTraceElement ste : new Exception().getStackTrace()) {
+                debug.println(" ".repeat(4) + ste);
+            }
+        }
         if (fStr != null && !fStr.isEmpty()) {
             tmpFilter = new Filter(fStr);
         }