Throw UncheckedIOException on directory creation errors

Previously, Config#mkdir and #mkAppDir threw ConfigException if any
underlying IOException was thrown from Files#createDirectory or
Files#createDirectories respectively. This resulted in only a simple
error message being reported at the command line and the details of the
underlying exception's stack trace were lost. This change wraps and
rethrows the underlying IOException as an UncheckedIOException such that
it gets caught by the catch(Throwable) clause in BisqExecutable, which
does print a stacktrace to stderr. This is the way it always should have
worked; throwing ConfigException in these cases was an oversight in the
original implementation. This change also removes the ConfigException
constructor that allows for passing a nested exception to be wrapped as
there is actually no use case for this now that these two anomalies have
been corrected.

This change was made in the process of attempting to reproduce bisq-network#3998.

common/src/main/java/bisq/common/config/Config.java

@@ -802,7 +802,7 @@ private static File mkAppDataDir(File appDataDir) {
         try {
             Files.createDirectories(path);
         } catch (IOException ex) {
-            throw new ConfigException(ex, "Application data directory '%s' could not be created", path);
+            throw new UncheckedIOException(format("Application data directory '%s' could not be created", path), ex);
         }
         return appDataDir;
     }
@@ -819,7 +819,7 @@ private static File mkdir(File parent, String child) {
             try {
                 Files.createDirectory(path);
             } catch (IOException ex) {
-                throw new ConfigException(ex, "Directory '%s' could not be created", path);
+                throw new UncheckedIOException(format("Directory '%s' could not be created", path), ex);
             }
         }
         return dir;

common/src/main/java/bisq/common/config/ConfigException.java

@@ -7,8 +7,4 @@ public class ConfigException extends BisqException {
     public ConfigException(String format, Object... args) {
         super(format, args);
     }
-
-    public ConfigException(Throwable cause, String format, Object... args) {
-        super(cause, format, args);
-    }
 }