Prefer installed

[nikolai-laevskii]

Description: Adds ability to set preference for already installed versions when setting up dotnet environment. If prefer-installed flag is active, action will attempt to check already installed versions with dotnet utility. If matching version exists on the runner, request for this specific version will be passed to the install-script, which has ability to verify already installed version and skip download if current installation is not broken.

Related issue: https://github.com/actions/setup-dotnet/issues/356

Check list:

• [x] Mark if documentation changes are required.
• [x] Mark if tests were added or updated to cover the changes.