Move Utf8String experiment to dotnet/runtimelab #3
Description
- Create Utf8String branch that is clone of dotnet/runtime
- (optional) Trim the the build in this branch so that it builds just ref pack, runtimepack and the Utf8String package, CoreCLR-only, no mono.
- Add lightweight pre-checkin CI that just builds say Windows and Linux, and runs tests on it
- Add post-commit CI that publishes ref pack, runtimepack and the Utf8String package into a new feed that we will setup for runtimelab packages.
- Add readme and notes for how to setup a new experiment (in dotnet/runtimelab:master)
- Delete the experimental code in dotnet/runtime