Revert "Migrate to use pub workspace"

This reverts commit b9b77058a9.


Revert "Add missing sample pubspec to workspace"

This reverts commit 892ea15ac7.


These seem to break the engine.

Change-Id: Ieee26deb7928c3869a1b6265326c3ce568ffe731
Tested: this is a revert.
CoreLibraryReviewExempt: this is a revert
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/415582
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>

pkg/testing/pubspec.yaml

@@ -7,8 +7,6 @@ publish_to: none
 environment:
   sdk: ^3.5.0
 
-resolution: workspace
-
 # Use 'any' constraints here; we get our versions from the DEPS file.
 dev_dependency:
   lints: any