Add .NET 9 target

[mus65]

I had to disable a SonarSource analyzer and made use of the new Lock type, see separate Commits.

CI is expected to fail because of missing .NET 9 binaries in AppVeyor. Build and tests pass locally.

Can be merged when .NET 9 final is released and AppVeyor supports it.

[Rob-Hague]

Can we have a basic Lock polyfill to save on the #ifdefs? e.g.

#if !NET9_0_OR_GREATERnamespaceRenci.SshNet.Common;internalsealedclassLock{publicboolTryEnter()=>Monitor.TryEnter(this);publicvoidExit()=>Monitor.Exit(this);}

[mus65]

Makes sense, pushed.

[drieseng]

@mus65, you'll also want to update global.json.

[drieseng]

@Rob-Hague, are planning on merging this before the release of .NET 9.0? In theory, there may even be API changes - I'm thinking of the Lock class - between now and the release. It's highly unlikely though.

[mus65]

@drieseng@Rob-Hague I updated global.json . I had to reference RC1 explicitly though, so I have to change it when final is released.

I left it a draft because it's still preview and wouldn't expect it to be merged before .NET 9 final. RC1 is already released, so I wouldn't expect any more API changes.

[Rob-Hague]

Yeah, we will merge once .NET 9 is released

Newer targets can be used on appveyor with apt-get, as in the opposite of #1352

[mus65]

This is now only blocked by AppVeyor not supporting .NET 9. apt-get is not going work either because the dotnet9 package is not available in Ubuntu 22.04 (see https://launchpad.net/ubuntu/+source/dotnet9 ).

@Rob-Hague has there been any thought about moving to GitHub actions?

[Rob-Hague]

I seem to remember @WojciechNagorski trying it but I can't find a PR so may be imagining

[Rob-Hague]

Feel free to give a go though