Add simple hex utils that delegate to Netty

The goal is to use libraries for this sort of common stuff

src/test/java/tools/HexToolTest.java

@@ -0,0 +1,22 @@
+package tools;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class HexToolTest {
+
+    @Test
+    void upperCaseHexToBytesAndBack() {
+        String hex = "A1B2C3";
+        byte[] bytes = HexTool.hexToBytes(hex);
+        assertEquals(hex, HexTool.bytesToHex(bytes));
+    }
+
+    @Test
+    void mixedCaseHexToBytesAndBack() {
+        String hex = "aB5DaA";
+        byte[] bytes = HexTool.hexToBytes(hex);
+        assertEquals(hex.toUpperCase(), HexTool.bytesToHex(bytes));
+    }
+}