Update all DockerFile for build image performance

src/EventHub.Admin.HttpApi.Host/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/publish/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.Admin.HttpApi.Host.dll"]

src/EventHub.BackgroundServices/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.BackgroundServices.dll"]

src/EventHub.DbMigrator/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.DbMigrator.dll"]

src/EventHub.HttpApi.Host/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/publish/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.HttpApi.Host.dll"]

src/EventHub.IdentityServer/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/publish/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.IdentityServer.dll"]

src/EventHub.Web/Dockerfile

@@ -1,4 +1,4 @@
-  FROM mcr.microsoft.com/dotnet/aspnet:6.0
+  FROM mcr.microsoft.com/dotnet/aspnet:6.0.0-rc.1-bullseye-slim
   COPY bin/Release/net6.0/publish/ app/
   WORKDIR /app
   ENTRYPOINT ["dotnet", "EventHub.Web.dll"]