Bump pub to 5b5fdd320a3b60a6a00bdd3122f03c6f67a39eeb

Changes:
```
> git log --format="%C(auto) %h %s" 4ab2e36..5b5fdd3
 https://dart.googlesource.com/pub.git/+/5b5fdd32 Do not show advisories text if no version is affected (4157)
 https://dart.googlesource.com/pub.git/+/4edf5cb2 Do not report ignored advisories in 'pub outdated' (4156)
 https://dart.googlesource.com/pub.git/+/c0e83746 Fix output of 'pub outdated' when there are several advisories (4158)
 https://dart.googlesource.com/pub.git/+/33e2b914 Make class private (4152)
 https://dart.googlesource.com/pub.git/+/c28f96a1 Prefer IPV4 on localhost, serve testserver on IPV4 (4149)
 https://dart.googlesource.com/pub.git/+/54293e3b Include info about security advisories in json output of `pub outdated` (4148)
 https://dart.googlesource.com/pub.git/+/48d3a544 Cleanup unused method (4147)
 https://dart.googlesource.com/pub.git/+/baa19b6c Make a RootDescription not depend on the root Package (4140)
 https://dart.googlesource.com/pub.git/+/93ce284d Surface security advisories in pub outdated (4136)
 https://dart.googlesource.com/pub.git/+/b1698df0 Always pass --git-dir when handling repoCache (4142)
 https://dart.googlesource.com/pub.git/+/d664d7f0 Devtools Extension validator (4135)
 https://dart.googlesource.com/pub.git/+/235e9421 Implement command "unpack" (4111)
 https://dart.googlesource.com/pub.git/+/f68b0e18 Remove stray comment (4137)
 https://dart.googlesource.com/pub.git/+/8c8814df Rename GitResolvedDescription to ResolvedGitDescription (4138)
 https://dart.googlesource.com/pub.git/+/3d285a39 Support for workspace syntax in pubspec.yaml (4128)
 https://dart.googlesource.com/pub.git/+/f8b23495 Update the repository specification (4134)
 https://dart.googlesource.com/pub.git/+/d948454f Bump dart-lang/setup-dart from 1.6.0 to 1.6.2 (4133)
 https://dart.googlesource.com/pub.git/+/465a45cd Bump checks from 0.2.2 to 0.3.0 (4132)

```

Diff: https://dart.googlesource.com/pub.git/+/4ab2e3663f0a98be40427e004e789caebf3ea72e..5b5fdd320a3b60a6a00bdd3122f03c6f67a39eeb/
Change-Id: I440f41b0e00c610d9e821b955345094c48dae8da
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/355421
Reviewed-by: Sarah Zakarias <zarah@google.com>
Commit-Queue: Sigurd Meldgaard <sigurdm@google.com>

CHANGELOG.md

@@ -36,11 +36,15 @@
 
 #### Pub
 
-- Dependency resolution will now surface if a dependency is affected by a
-  security advisory, unless the advisory is listed under a
-  `ignored_advisories` section in the `pubspec.yaml` file.
-  To learn more about pub's support for security advisories,
-  visit [dart.dev/go/pub-security-advisories][pub-security-advisories].
+- Dependency resolution and `dart pub outdated` will now surface if a dependency
+  is affected by a security advisory, unless the advisory is listed under a
+  `ignored_advisories` section in the `pubspec.yaml` file. To learn more about
+  pub's support for security advisories, visit
+  [dart.dev/go/pub-security-advisories][pub-security-advisories].
+- New command `dart pub unpack` that downloads a package from pub.dev and
+  extracts it to a subfolder of the current directory.
+
+  This can be useful for inspecting the code, or playing with examples.
 
 [pub-security-advisories]: https://dart.dev/go/pub-security-advisories
 

DEPS

@@ -168,7 +168,7 @@ vars = {
   "path_rev": "a7b696071bd83d3ee0a0f1b57ac94d6b1f05cac4",
   "pool_rev": "782da82fedca4e5776e43ba321543ed2b20373b2",
   "protobuf_rev": "ef0ab7df985a4b00f3a6850fb160a214ebc0683e",
-  "pub_rev": "4ab2e3663f0a98be40427e004e789caebf3ea72e", # disable rev_sdk_deps.dart
+  "pub_rev": "5b5fdd320a3b60a6a00bdd3122f03c6f67a39eeb", # disable rev_sdk_deps.dart
   "pub_semver_rev": "3175ba0a58a96fb23f8d68b5f5c44d1a5b30cc16",
   "shelf_rev": "b432620f109b92c0399261722aa28c4d8d9a385c",
   "source_map_stack_trace_rev": "c75649651d01826236e3ab7093d277a70756905a",