Removed xamarin related. Revised .NET SDK detection. · lextudio/sharpsnmplib@c9c5c05

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions/setup-dotnet@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v2, actions/setup-dotnet@v1, coverallsapp/github-action@master. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

Build: SharpSnmpLib/Messaging/Net6Discoverer.cs#L26

Remove this empty namespace. (https://rules.sonarsource.com/csharp/RSPEC-3261)

Build: SharpSnmpLib/OperationException.cs#L39

Update this implementation of 'ISerializable' to conform to the recommended serialization pattern. Make the serialization constructor 'protected'. (https://rules.sonarsource.com/csharp/RSPEC-3925)

Build: SharpSnmpLib/Security/TripleDESPrivacyProvider.cs#L419

Make 'ExtendShortKey' a static method. (https://rules.sonarsource.com/csharp/RSPEC-2325)

Build: SharpSnmpLib/Security/SHA512AuthenticationProvider.cs#L92