Add tests for different Postgres client libraries (#2008)

* Add tests for different postgres clients
* test/fixtures: sanitize test name for test_output_dir
* test/fixtures: do not look for etcd before runtime
* Add workflow for testing Postgres client libraries

test_runner/pg_clients/csharp/npgsql/Dockerfile

@@ -0,0 +1,14 @@
+FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build
+WORKDIR /source
+
+COPY *.csproj .
+RUN dotnet restore
+
+COPY . .
+RUN dotnet publish -c release -o /app --no-restore
+
+FROM mcr.microsoft.com/dotnet/runtime:6.0
+WORKDIR /app
+COPY --from=build /app .
+
+ENTRYPOINT ["dotnet", "csharp-npgsql.dll"]