Remove Cpp Client from this repo (#9050)

.azure/pipelines/ci.yml

.azure/pipelines/signalr-daily-tests.yml

build/repo.props

src/SignalR/.gitmodules

src/SignalR/clients/cpp/.gitignore

src/SignalR/clients/cpp/Build/Common.Build.Settings

src/SignalR/clients/cpp/Build/Common.tasks

src/SignalR/clients/cpp/Build/Config.Definitions.Props

src/SignalR/clients/cpp/Build/SignalRClient.Build.Settings

src/SignalR/clients/cpp/Build/Version.props

src/SignalR/clients/cpp/Build/build.msbuild

src/SignalR/clients/cpp/CMakeLists.txt

src/SignalR/clients/cpp/CONTRIBUTING.md

src/SignalR/clients/cpp/NuGet.config

.../Microsoft.AspNet.SignalR.Client.Cpp.UWP.targets.template

...oft.AspNet.SignalR.Client.Cpp.WinDesktop.targets.template

...ignalR/clients/cpp/NuGet/signalrclientcpp.nuspec.template

src/SignalR/clients/cpp/README.md

src/SignalR/clients/cpp/build.cmd

src/SignalR/clients/cpp/include/signalrclient/_exports.h