Tracing: added customizable verbosity level

As some gathered data can be heavy or sensitive or we might want
to not have them in the trace for some reason, verbosity level layer
has been added. Currently, statement is both possibly long
and containing some sensitive data, so it is included only on level
FULL (and not NORMAL).

Author: wprzytula

driver-core/src/main/java/com/datastax/driver/core/tracing/VerbosityLevel.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2021 ScyllaDB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.datastax.driver.core.tracing;
+
+/** The verbosity level of tracing data that is to be collected. May be extended in the future. */
+public enum VerbosityLevel {
+  // Enum elements must be listed in ascending order of verbosity level (i.e. each next element
+  // listed adds some new information).
+  NORMAL,
+  FULL;
+}