feat(virtdata): reify a per-cycle statement form as a prepared fragment

A bind value that is part statement and part parameters: text with
positional markers, the values for them, and the key of the form the
text has. Equal keys mean equal text, so an adapter prepares each form
once and binds every later fragment of that form through it.

nb-virtdata/virtdata-api/src/main/java/io/nosqlbench/virtdata/core/templates/PreparedFragment.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) nosqlbench
+ *
+ * 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 io.nosqlbench.virtdata.core.templates;
+
+import java.util.Arrays;
+
+/// A bind value that is part statement and part parameters: text with
+/// positional markers, the values that fill them, and the identity of
+/// the **form** the text has.
+///
+/// A binding that produces fragments reifies a structure that changes
+/// per cycle — a predicate whose shape differs from one query to the
+/// next — into statement text an adapter can prepare, while the values
+/// still bind as parameters. Two fragments with the same [#formKey]
+/// have the same [#text], so an adapter prepares each form once and
+/// binds every later fragment of that form through the statement it
+/// already holds. The key is whatever identifies the form to its
+/// producer; for a predicate it is the node's fingerprint.
+public interface PreparedFragment {
+
+    /// The identity of this fragment's form. Equal keys mean equal text.
+    String formKey();
+
+    /// The statement text of the form, with a `?` per value.
+    String text();
+
+    /// The values for the markers, in marker order.
+    Object[] values();
+
+    /// A fragment of its three parts.
+    static PreparedFragment of(String formKey, String text, Object[] values) { return new Of(formKey, text, values); }
+
+    /// The plain fragment.
+    record Of(String formKey, String text, Object[] values) implements PreparedFragment {
+        @Override public String toString() { return "Fragment[" + text + " <- " + Arrays.toString(values) + "]"; }
+    }
+}