Fold timing into build_runner. (#4192)

Author: davidmorgan

build_runner/CHANGELOG.md

@@ -3,7 +3,8 @@
 - Bug fix: fix incorrect display of some "usage" messages.
 - Move code from `build_resolvers` into `build_runner`.
 - Move code from `build_runner_core` into `build_runner`.
-- Remove unused deps: `build_resolvers`, `build_runner_core`.
+- Move code from `timing` into `build_runner`.
+- Remove unused deps: `build_resolvers`, `build_runner_core`, `timing`.
 
 ## 2.7.2
 

build_runner/lib/src/generate/performance_tracker.dart

@@ -10,10 +10,10 @@ import 'dart:async';
 import 'package:build/build.dart';
 import 'package:json_annotation/json_annotation.dart';
 import 'package:meta/meta.dart';
-import 'package:timing/timing.dart';
 
 import 'phase.dart';
 import 'run_builder.dart';
+import 'timing.dart';
 
 part 'performance_tracker.g.dart';