fix: Add thread logging

Author: MichaelsJP

core/src/main/java/com/graphhopper/routing/ch/CHPreparationHandler.java

@@ -179,6 +179,7 @@ public int getPreparationThreads() {
      */
     public void setPreparationThreads(int preparationThreads) {
         this.preparationThreads = preparationThreads;
+        LOGGER.info("Using {} threads for ch preparation threads", preparationThreads);
         this.threadPool = java.util.concurrent.Executors.newFixedThreadPool(preparationThreads);
     }
 

core/src/main/java/com/graphhopper/routing/lm/LMPreparationHandler.java

@@ -136,6 +136,7 @@ public int getPreparationThreads() {
      */
     public void setPreparationThreads(int preparationThreads) {
         this.preparationThreads = preparationThreads;
+        LOGGER.info("Using {} threads for lm preparation threads", preparationThreads);
         this.threadPool = java.util.concurrent.Executors.newFixedThreadPool(preparationThreads);
     }