Reland "Sync packages from shelf mono repo"

This is a reland of commit 072603d40a2129a0a78629f5f55025d453cabeee

Original change's description:
> Sync packages from shelf mono repo
>
> Drop the DEPS entries for the repositories which will be archived. Each
> of the packages has been merged into the `shelf` repository.
>
> Add the `shelf` repository to the specially handled directories with
> nested packages in `generate_package_config`.
>
> Update path dependencies in pubspecs to the new location.
>
> R=devoncarew@google.com
>
> Change-Id: Iefca4fdb2abb6bafa273b9b6b1b4f25d6c91b005
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/243929
> Reviewed-by: Alexander Thomas <athom@google.com>
> Reviewed-by: Devon Carew <devoncarew@google.com>
> Commit-Queue: Nate Bosch <nbosch@google.com>
> Auto-Submit: Nate Bosch <nbosch@google.com>

Change-Id: I064d9bc87263e02357021c1def2b656afe45cf22
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/244725
Reviewed-by: Devon Carew <devoncarew@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>
Auto-Submit: Nate Bosch <nbosch@google.com>
diff --git a/DEPS b/DEPS
index e5dbeb3..d151715 100644
--- a/DEPS
+++ b/DEPS
@@ -142,11 +142,7 @@
   "pub_semver_rev": "ea6c54019948dc03042c595ce9413e17aaf7aa38",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",
   "rust_revision": "b7856f695d65a8ebc846754f97d15814bcb1c244",
-  "shelf_packages_handler_rev": "78302e67c035047e6348e692b0c1182131f0fe35",
-  "shelf_proxy_rev": "124615d0614b38814970aa9638725d9d6b435268",
-  "shelf_rev": "78ac724a7944700340a3cef28c84bccbe62e9367",
-  "shelf_static_rev": "202ec1a53c9a830c17cf3b718d089cf7eba568ad",
-  "shelf_web_socket_rev": "24fb8a04befa75a94ac63a27047b231d1a22aab4",
+  "shelf_rev": "fadca320b04689be9ec960013843a0d9ee6c4fc4",
   "source_map_stack_trace_rev": "8eabd96b1811e30a11d3c54c9b4afae4fb72e98f",
   "source_maps_rev": "c07a01b8d5547ce3a47ee7a7a2b938a2bc09afe3",
   "source_span_rev": "8ae724c3e67f5afaacead44e93ff145bfb8775c7",
@@ -393,16 +389,6 @@
       Var("dart_git") + "pub.git" + "@" + Var("pub_rev"),
   Var("dart_root") + "/third_party/pkg/shelf":
       Var("dart_git") + "shelf.git" + "@" + Var("shelf_rev"),
-  Var("dart_root") + "/third_party/pkg/shelf_packages_handler":
-      Var("dart_git") + "shelf_packages_handler.git"
-      + "@" + Var("shelf_packages_handler_rev"),
-  Var("dart_root") + "/third_party/pkg/shelf_proxy":
-      Var("dart_git") + "shelf_proxy.git" + "@" + Var("shelf_proxy_rev"),
-  Var("dart_root") + "/third_party/pkg/shelf_static":
-      Var("dart_git") + "shelf_static.git" + "@" + Var("shelf_static_rev"),
-  Var("dart_root") + "/third_party/pkg/shelf_web_socket":
-      Var("dart_git") + "shelf_web_socket.git" +
-      "@" + Var("shelf_web_socket_rev"),
   Var("dart_root") + "/third_party/pkg/source_maps":
       Var("dart_git") + "source_maps.git" + "@" + Var("source_maps_rev"),
   Var("dart_root") + "/third_party/pkg/source_span":
diff --git a/pkg/compiler/pubspec.yaml b/pkg/compiler/pubspec.yaml
index cb44cf3..d2e8bbb 100644
--- a/pkg/compiler/pubspec.yaml
+++ b/pkg/compiler/pubspec.yaml
@@ -98,9 +98,9 @@
   protobuf:
     path: ../../third_party/pkg/protobuf/protobuf
   shelf:
-    path: ../../third_party/pkg/shelf
+    path: ../../third_party/pkg/shelf/pkgs/shelf
   shelf_static:
-    path: ../../third_party/pkg/shelf_static
+    path: ../../third_party/pkg/shelf/pkgs/shelf_static
   source_span:
     path: ../../third_party/pkg/source_span
   stack_trace:
diff --git a/pkg/dev_compiler/pubspec.yaml b/pkg/dev_compiler/pubspec.yaml
index 90c1a69..9ff430c 100644
--- a/pkg/dev_compiler/pubspec.yaml
+++ b/pkg/dev_compiler/pubspec.yaml
@@ -52,6 +52,6 @@
   meta:
     path: ../meta
   shelf:
-    path: ../../third_party/pkg/shelf
+    path: ../../third_party/pkg/shelf/pkgs/shelf
   http_multi_server:
     path: ../../third_party/pkg/http_multi_server
diff --git a/tools/generate_package_config.dart b/tools/generate_package_config.dart
index 150f06f..536a5b6 100644
--- a/tools/generate_package_config.dart
+++ b/tools/generate_package_config.dart
@@ -20,6 +20,7 @@
     ...listSubdirectories(platform('third_party/pkg')),
     ...listSubdirectories(platform('third_party/pkg/file/packages')),
     ...listSubdirectories(platform('third_party/pkg/test/pkgs')),
+    ...listSubdirectories(platform('third_party/pkg/shelf/pkgs')),
     platform('pkg/vm_service/test/test_package'),
     platform('runtime/observatory_2'),
     platform(