Java/Shared: Add caching to the CFG library.

Author: aschackmull

java/ql/lib/semmle/code/java/ControlFlowGraph.qll

@@ -9,21 +9,16 @@ private import codeql.controlflow.ControlFlowGraph
 private import codeql.controlflow.SuccessorType
 private import controlflow.internal.Preconditions
 
-private module ControlFlow0 = Make0<Location, Ast>;
+private module Cfg0 = Make0<Location, Ast>;
 
-private module ControlFlow1 = Make1<Input>;
+private module Cfg1 = Make1<Input>;
 
-private module ControlFlow2 = Make2<Input>;
+private module Cfg2 = Make2<Input>;
 
-private import ControlFlow0
-private import ControlFlow1
-import ControlFlow2 as ControlFlow
-
-class ControlFlowNode = ControlFlow::ControlFlowNode;
-
-module Cfg = ControlFlow::Cfg;
-
-import Cfg
+private import Cfg0
+private import Cfg1
+private import Cfg2
+import Public
 
 /** Provides an implementation of the AST signature for Java. */
 module Ast implements AstSig<Location> {
@@ -434,6 +429,8 @@ private module NonReturningCalls {
 private module Input implements InputSig1, InputSig2 {
   private import java as J
 
+  predicate cfgCachedStageRef() { CfgCachedStage::ref() }
+
   /** Holds if this catch clause catches all exceptions. */
   predicate catchAll(Ast::CatchClause catch) {
     catch.getACaughtType() instanceof TypeThrowable