Revert "Move BytesBuilder class and implementation to dart:typed_data."

This reverts commit 084f9fa.

Reason for revert: Breaks ABI without relevant version updates 

Original change's description:
> Move `BytesBuilder` class and implementation to `dart:typed_data`.
> 
> Change-Id: I3e66e61940a1060e4970427799e0d8ebdaebb310
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150523
> Commit-Queue: Lasse R.H. Nielsen <lrn@google.com>
> Reviewed-by: Nate Bosch <nbosch@google.com>

TBR=lrn@google.com,nbosch@google.com

Change-Id: I2b79063b7ff70de7ce039283a10d56460594a6ab
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154563
Reviewed-by: Ryan Macnak <rmacnak@google.com>

Author: rmacnak-google

CHANGELOG.md

@@ -58,11 +58,6 @@
 
 [#41653]: https://github.com/dart-lang/sdk/issues/41653
 
-#### `dart:typed_data`
-
-*   Class `BytesBuilder` originally from `dart:io` is now available
-    in `dart:typed_data`. It's still exported from `dart:io` as well.
-
 ### Tools
 
 #### dartfmt

sdk/lib/_internal/vm/bin/common_patch.dart

@@ -33,7 +33,7 @@ import "dart:math" show min;
 
 import "dart:nativewrappers" show NativeFieldWrapperClass1;
 
-import "dart:typed_data" show Uint8List, BytesBuilder;
+import "dart:typed_data" show Uint8List;
 
 /// These are the additional parts of this patch library:
 // part "directory_patch.dart";

sdk/lib/internal/bytes_builder.dart

@@ -21,7 +21,6 @@ import 'dart:math' show Random;
 import 'dart:typed_data' show Uint8List;
 
 part 'async_cast.dart';
-part 'bytes_builder.dart';
 part 'cast.dart';
 part 'errors.dart';
 part 'iterable.dart';

sdk/lib/internal/internal.dart

@@ -8,7 +8,6 @@ internal_sdk_sources = [
 
   # The above file needs to be first as it lists the parts below.
   "async_cast.dart",
-  "bytes_builder.dart",
   "cast.dart",
   "errors.dart",
   "iterable.dart",