Capture all logs and errors in the Pantheon log output (#1437)

* Add slf4j to log4j bindings as a runtime dependency so any libraries that log to slf4j have their logs output to Pantheon's logs properly.

* Set a default exception handler to ensure uncaught exceptions wind up in the Pantheon logs.

pantheon/build.gradle

@@ -54,6 +54,7 @@ dependencies {
   implementation 'org.springframework.security:spring-security-crypto'
 
   runtime 'org.apache.logging.log4j:log4j-core'
+  runtime 'org.apache.logging.log4j:log4j-slf4j-impl'
 
   testImplementation project(':testutil')
   testImplementation project(path: ':ethereum:core', configuration: 'testSupportArtifacts')

pantheon/src/main/java/tech/pegasys/pantheon/Pantheon.java

@@ -21,17 +21,21 @@
 import tech.pegasys.pantheon.services.kvstore.RocksDbConfiguration;
 import tech.pegasys.pantheon.util.BlockImporter;
 
+import org.apache.logging.log4j.Logger;
 import picocli.CommandLine.RunLast;
 
 public final class Pantheon {
   private static final int SUCCESS_EXIT_CODE = 0;
   private static final int ERROR_EXIT_CODE = 1;
 
   public static void main(final String... args) {
-
+    final Logger logger = getLogger();
+    Thread.setDefaultUncaughtExceptionHandler(
+        (thread, error) ->
+            logger.error("Uncaught exception in thread \"" + thread.getName() + "\"", error));
     final PantheonCommand pantheonCommand =
         new PantheonCommand(
-            getLogger(),
+            logger,
             new BlockImporter(),
             new RunnerBuilder(),
             new PantheonController.Builder(),