Adds new package:sse dependency

1e78bd069e [ package:dds ] Add missing package:shelf_static dependency in pubspec.yaml
51d3fae7d3 Revert "Move `BytesBuilder` class and implementation to `dart:typed_data`."
e7b319698d [ package:dds ] Add server-sent event (SSE) support to DDS
d4ac7066b7 Improve diagnostic message when short circuiting (issue 42599)
7960ad545a [ Service ] Fix line numbers in step_through_mixin_from_sdk_test
505fca1ce5 [ package:dds ] Fix issue where StateError could be thrown if DDS shuts down with in-flight requests
47b080de23 [vm/nnbd] Do not check if NNBD experimental flag is enabled for non-null assertions
ef147c0a95 Issue 42699. Stop reporting EXPORT_DUPLICATED_LIBRARY_NAMED and IMPORT_DUPLICATED_LIBRARY_NAMED.
0cc2d9685a [vm] Fix --use-bare-instructions=false on simarm_x64.
6fc75e6a2b [vm] Add tests and packages to the Fuchsia package
a2edb7976c Make CiderCacheEntry public.
4726b1b337 [infra] Update Chrome used in testing to version 84