Update builds / docs after next SharpFuzz release

[ranweiler]

After the changes in Metalnem/sharpfuzz#24 are published to NuGet, update the following:

• Depend on a published SharpFuzz package in LibFuzzerDotnetLoader (instead of a local path)
• Update dotnet-fuzzing-tools.{ps1,sh} to match
• Remove pre-release instructions from the LibFuzzerDotnetLoader README

AB#40376873