Retry `ClientException` from `package:http`

[jonasfj]

We should probably also retry ClientException from package:http:

https://github.com/dart-lang/pub-dev/blob/031c368ea0840f2bdcf2bcaee7886a13c19b90b4/app/lib/shared/storage.dart#L142-L154

[isoos]

I think we should refactor/merge the various retry methods we have to make sure every one of them uses the same retry logic. Keeping this issue open to track that.

[isoos]

Another case in storage access:

Error:
    ClientException: Connection closed before full header was received, uri=https://storage.googleapis.com/storage/v1/b/dartlang-pub-exported-api/o/latest%2Fapi%2Farchives%2Fstacked-2.3.14.tar.gz?projection=full&alt=json

Stack:
    #0      IOClient.send (package:http/src/io_client.dart:156:7)
    <asynchronous suspension>
    #1      AuthenticatedClient.send (package:googleapis_auth/src/auth_http_utils.dart:41:22)
    <asynchronous suspension>
    #2      RetryClient.send (package:http/retry.dart:115:20)
    <asynchronous suspension>
    #3      ApiRequester.request (package:_discoveryapis_commons/src/api_requester.dart:69:20)
    <asynchronous suspension>
    #4      ObjectsResource.get (package:googleapis/storage/v1.dart:3422:23)
    <asynchronous suspension>
    #5      _BucketImpl.info.<anonymous closure> (package:gcloud/src/storage_impl.dart:255:15)
    <asynchronous suspension>
    #6      BucketExt.tryInfo (package:pub_dev/shared/storage.dart:79:14)
    <asynchronous suspension>
    #7      ExportedApi._findStrayFiles.<anonymous closure> (package:pub_dev/package/api_export/exported_api.dart:215:11)
    <asynchronous suspension>