stable null safety release, clean up deps (#105)

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 5903bc8..4f74712 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: package_config
-version: 2.0.0-nullsafety.1
+version: 2.0.0
 description: Support for working with Package Configuration files.
 homepage: https://github.com/dart-lang/package_config
 
@@ -7,53 +7,17 @@
   sdk: '>=2.12.0-0 <3.0.0'
 
 dependencies:
-  path: ^1.8.0-nullsafety.3
+  path: ^1.8.0
 
 dev_dependencies:
-  build_resolvers: ^1.10.0
   build_runner: ^1.10.0
-  build_runner_core: ^1.10.0
   build_test: ^1.3.0
-  build_web_compilers: ^2.15.0
-  pedantic: ^1.10.0-nullsafety.3
-  test: ^1.16.0-nullsafety.4
+  build_web_compilers: ^2.12.2
+  pedantic: ^1.10.0-nullsafety.0
+  test: ^1.16.0-nullsafety.19
 
+# Required due to dependency cycles
 dependency_overrides:
-  _fe_analyzer_shared:
-    git:
-      url: git://github.com/dart-lang/sdk.git
-      path: pkg/_fe_analyzer_shared
-  analyzer:
-    git:
-      url: git://github.com/dart-lang/sdk.git
-      path: pkg/analyzer
-  build_resolvers:
-    git:
-      url: git://github.com/dart-lang/build.git
-      path: build_resolvers
-  build_runner:
-    git:
-      url: git://github.com/dart-lang/build.git
-      path: build_runner
-  build_runner_core:
-    git:
-      url: git://github.com/dart-lang/build.git
-      path: build_runner_core
-  build_test:
-    git:
-      url: git://github.com/dart-lang/build.git
-      path: build_test
-  coverage:
-    git: git://github.com/dart-lang/coverage.git
-  test:
-    git:
-      url: git://github.com/dart-lang/test.git
-      path: pkgs/test
-  test_api:
-    git:
-      url: git://github.com/dart-lang/test.git
-      path: pkgs/test_api
-  test_core:
-    git:
-      url: git://github.com/dart-lang/test.git
-      path: pkgs/test_core
+  test: ^1.16.0-nullsafety.19
+  coverage: ^0.15.1
+  analyzer: ^0.41.0