Add Java RE needed for dotnet sonar scanner execution
Install .net6.0 from Microsoft's PMR
Use ubuntu base image
Potential fix by not using custom package repositories and removing gpg instruction
Set base image to net5.0 (needed by dotnet-sonarscanner) and install net6.0 sdk alongside it
Upgrade to latest dotnet scanner utility 5.12.0
Upgrade to use net6.0 sdk base image
Sonar scan utility that supports .netcoreapp3.1