[cfe] Move general testcases into general/ subfolder

Change-Id: I9bc98033babcf887cca2267606cfe9fadd527b5f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108605
Reviewed-by: Jens Johansen <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: johnniwinther

pkg/front_end/test/fasta/incremental_hello_test.dart

@@ -49,7 +49,8 @@ test({bool sdkFromSource}) async {
             .resolve("vm_platform.dill");
   }
 
-  final Uri helloDart = Uri.base.resolve("pkg/front_end/testcases/hello.dart");
+  final Uri helloDart =
+      Uri.base.resolve("pkg/front_end/testcases/general/hello.dart");
 
   final ProcessedOptions options =
       new ProcessedOptions(options: optionBuilder, inputs: [helloDart]);