Switch to an abstract unit / predicate approach to specifying rows to generate tests for

This enables moving this code into the qll file, rather than having to specify a query predicate in the .ql

Author: smowton

java/ql/src/utils/GenerateFlowTestCase.py

@@ -112,7 +112,7 @@ def qualifiedOuterNameFromSsvRow(row):
 with open(os.path.join(queryDir, "qlpack.yml"), "w") as f:
   f.write("name: test-generation-query\nversion: 0.0.0\nlibraryPathDependencies: codeql-java")
 with open(qlFile, "w") as f:
-  f.write("import java\nimport utils.GenerateFlowTestCase\n\nclass GenRow extends CsvRow {\n\n\tGenRow() {\n\t\tthis = [\n")
+  f.write("import java\nimport utils.GenerateFlowTestCase\n\nclass GenRow extends TargetSummaryModelCsv {\n\n\toverride predicate row(string r) {\n\t\tr = [\n")
   f.write(",\n".join('\t\t\t"%s"' % spec.strip() for spec in specs))
   f.write("\n\t\t]\n\t}\n}\n")
 

java/ql/src/utils/GenerateFlowTestCase.qll

@@ -8,23 +8,26 @@ import semmle.code.java.dataflow.internal.FlowSummaryImpl
  * A CSV row to generate tests for. Users should extend this to define which
  * tests to generate. Rows specified here should also satisfy `SummaryModelCsv.row`.
  */
-bindingset[this]
-abstract class TargetSummaryModelCsv extends string {
-  predicate modelRowExists() { any(SummaryModelCsv smc).row(this) }
+class TargetSummaryModelCsv extends Unit {
+  abstract predicate row(string r);
 }
 
 /**
  * Gets a CSV row for which a test has been requested, but `SummaryModelCsv.row` does not hold of it.
  */
-query TargetSummaryModelCsv missingSummaryModelCsv() { not result.modelRowExists() }
+query string missingSummaryModelCsv() {
+  any(TargetSummaryModelCsv target).row(result) and
+  not any(SummaryModelCsv model).row(result)
+}
 
 /**
  * Gets a CSV row for which a test has been requested, and `SummaryModelCsv.row` does hold, but
  * nonetheless we can't generate a test case for it, indicating we cannot resolve either the callable
  * spec or an input or output spec.
  */
-query TargetSummaryModelCsv getAParseFailure(string reason) {
-  result.modelRowExists() and
+query string getAParseFailure(string reason) {
+  any(TargetSummaryModelCsv target).row(result) and
+  any(SummaryModelCsv model).row(result) and
   (
     exists(
       string namespace, string type, boolean subtypes, string name, string signature, string ext