Bump pub to 42819a1e10f803eb7f6296692c5a976e1c647360

Changes:
```
> git log --format="%C(auto) %h %s" 078c7fe..42819a1
 https://dart.googlesource.com/pub.git/+/42819a1e Add missing await (and make downstream async) (3949)
 https://dart.googlesource.com/pub.git/+/c5c34c3e Add (more) trailing commas (3950)
 https://dart.googlesource.com/pub.git/+/a76c7916 Handle non-default hosts in `upgrade --major-versions` (3947)
 https://dart.googlesource.com/pub.git/+/a42800e5 Smallest update in `dependency-services report` (3761)
 https://dart.googlesource.com/pub.git/+/1be821d5 Remove usage of Isolate.packageRoot from tests (3945)
 https://dart.googlesource.com/pub.git/+/a16763a9 Validate that dependency names are valid package names (3940)
 https://dart.googlesource.com/pub.git/+/4a109f30 Expand constraint for `http` (3930)
 https://dart.googlesource.com/pub.git/+/8aee9515 Retry package:http ClientException (3939)
 https://dart.googlesource.com/pub.git/+/d7fa780d Add test for publish --skip-validation (3935)
 https://dart.googlesource.com/pub.git/+/5a3f21b4 Add strict-cast analysis option (3919)
 https://dart.googlesource.com/pub.git/+/fbb6f750 Merge pull request 3934 from sigurdm/cherry_pick_cache_warning
 https://dart.googlesource.com/pub.git/+/0dc18c02 Merge remote-tracking branch 'origin/master' into cherry_pick_cache_warning
 https://dart.googlesource.com/pub.git/+/fe6acca8 Warn about presence of legacy cache (3921)
 https://dart.googlesource.com/pub.git/+/0c2b0bb8 Handle pubspec_overrides.yaml in `add` and `upgrade --major-versions` (3920)
 https://dart.googlesource.com/pub.git/+/3a7dc04e Reinterpret dart sdk constraints when read from a lockfile (3897)

```

Diff: https://dart.googlesource.com/pub.git/+/078c7fea0be2656debc675646806da14fa94f853..42819a1e10f803eb7f6296692c5a976e1c647360/
Change-Id: Ic5a9b1fc1f03f029a36a208e31d919e5e82f0302
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/310881
Reviewed-by: Jonas Jensen <[email protected]>
Commit-Queue: Sigurd Meldgaard <[email protected]>

Author: sigurdm

DEPS

@@ -163,7 +163,7 @@ vars = {
   "path_rev": "592505f67d0563f72c933c2ba100ea7d4f3cb873",
   "pool_rev": "c6b1b2c22663c084a82c9bfe409c196fb38eea53",
   "protobuf_rev": "e76bd74e5c99b47c12b523b49140b637225fc3fc",
-  "pub_rev": "078c7fea0be2656debc675646806da14fa94f853", # disable rev_sdk_deps.dart
+  "pub_rev": "42819a1e10f803eb7f6296692c5a976e1c647360", # disable rev_sdk_deps.dart
   "pub_semver_rev": "3930557ee0b20ef528713952c318139409edadb4",
   "shelf_rev": "ce379aa3c22024edb2df3657fd564f1f463406e6",
   "source_map_stack_trace_rev": "b83af01938225c1706bbc6c1f86bd4a394f91380",