Rename "pathos" package to "path".

pkg/stack_trace/test/trace_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trace_test;
 
-import 'package:pathos/path.dart' as path;
+import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:unittest/unittest.dart';
 
 String getStackTraceString() {
   try {
     throw '';
   } catch (_, stackTrace) {
     return stackTrace.toString();
   }
 }
@@ skipping 164 matching lines @@
 
     var folded = trace.foldFrames((frame) => frame.member.startsWith('foo'));
     expect(folded.toString(), equals('''
 foo.dart 42:21                     notFoo
 foo.dart 1:100                     fooBottom
 bar.dart 10:20                     alsoNotFoo
 dart:async-patch/future.dart 9:11  fooBottom
 '''));
   });
 }