Add release/2.0.0 branch to perf runs
Add release/2.0.0 branch to perf runs

This turns on performance runs for both CoreFX and CoreCLR on the
release/2.0.0 branches.

dotnet/dotnet-ci,mmitche/dotnet-ci,dotnet/dotnet-ci,mmitche/dotnet-ci,tannergooding/dotnet-ci,tannergooding/dotnet-ci