Roll in `Metadata` json removal.
Roll in json snake casing.
TEST=pkg/compiler/test/record_use/record_use_test.dart
TEST=pkg/vm/test/transformations/record_use_test.dart
Change-Id: I16be8a48c7349c27faf82f308235961217fdd77a
Cq-Include-Trybots: luci.dart.try:pkg-linux-debug-try,pkg-linux-release-arm64-try,pkg-linux-release-try,pkg-mac-release-arm64-try,pkg-mac-release-try,pkg-win-release-arm64-try,pkg-win-release-try,dart2js-linux-chrome-try,dart2js-unit-linux-x64-release-try,dart2wasm-linux-jscm-chrome-try,dart2wasm-linux-optimized-jsc-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/474400
Reviewed-by: Michael Goderbauer <goderbauer@google.com>
Reviewed-by: Moritz Sümmermann <mosum@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Daco Harkes
211ff370c4