CI support for .NET 6.0 builds, tests and Nuget

[mregen]

• Add pipeline steps with VS2022 hosted images and .NET 6 install on linux/mac
• Nuget build with net6.0 binaries

[mregen]

Nuget test build available in Preview feed as 1.4.367-preview.g90173c71ed

[codecov]

Codecov Report

Merging #1580 (547a5f9) into master (7acddc0) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 547a5f9 differs from pull request most recent head c493fbe. Consider uploading reports for the commit c493fbe to get more accurate results

@@            Coverage Diff             @@
##           master    #1580      +/-   ##
==========================================
+ Coverage   52.89%   52.92%   +0.02%     
==========================================
  Files         312      312              
  Lines       57316    57316              
==========================================
+ Hits        30317    30333      +16     
+ Misses      26999    26983      -16     

Impacted Files	Coverage Δ
...raries/Opc.Ua.PubSub/Transport/UdpClientCreator.cs	18.47% <100.00%> (ø)
...ack/Opc.Ua.Core/Security/Certificates/X509Utils.cs	80.45% <0.00%> (-2.88%)	⬇️
...a.Core/Security/Certificates/CertificateFactory.cs	86.15% <0.00%> (-0.77%)	⬇️
Stack/Opc.Ua.Core/Stack/State/BaseInstanceState.cs	26.57% <0.00%> (-0.46%)	⬇️
...Security/Certificates/DirectoryCertificateStore.cs	90.03% <0.00%> (-0.34%)	⬇️
...ies/Opc.Ua.Server/Diagnostics/CustomNodeManager.cs	51.05% <0.00%> (+0.12%)	⬆️
Libraries/Opc.Ua.Server/Server/StandardServer.cs	52.61% <0.00%> (+0.34%)	⬆️
...tack/Opc.Ua.Core/Stack/Tcp/TcpTransportListener.cs	72.54% <0.00%> (+0.39%)	⬆️
...ies/Opc.Ua.Server/NodeManager/MasterNodeManager.cs	53.98% <0.00%> (+0.58%)	⬆️
Libraries/Opc.Ua.Client/NodeCache.cs	25.65% <0.00%> (+4.34%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7acddc0...c493fbe. Read the comment docs.

[mregen]

Hi @mrsuciu , some Pubsub test still not passing on mac/linux .. investigating