8186694: JShell: speed-up compilation by reusing compiler instances

Generalizing ReusableContext and using it in JShell to speed up processing.

Reviewed-by: mcimadamore, rfield

test/langtools/tools/javac/lambda/MethodReferenceParserTest.java

@@ -203,9 +203,9 @@ public class MethodReferenceParserTest extends ComboInstance<MethodReferencePars
 
     @Override
     public void doWork() throws IOException {
-        check(newCompilationTask()
+        newCompilationTask()
                 .withSourceFromTemplate(template)
-                .parse());
+                .parse(this::check);
     }
 
     void check(Result<?> res) {