Use FrameworkReference for kestrel package for .NET Core App >= 3.1

[mregen]

• Kestrel server is end of life for .NET Core 2.1, only support for .NET framework and netstandard2.0
• Use FrameworkReference to include ASPNET services in .NET Core 3.x and later
• adjust the code signing
• deprecate complextypes.symbols
• TODO: test if the wrapper packages can still include binding.https, it may cause issues when TargetFrameworks are different for the referenced packages.

[codecov]

Codecov Report

Merging #1646 (e6c411c) into master (5bcadf4) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1646      +/-   ##
==========================================
- Coverage   53.68%   53.67%   -0.01%     
==========================================
  Files         319      319              
  Lines       57740    57744       +4     
==========================================
- Hits        30996    30995       -1     
- Misses      26744    26749       +5     

Impacted Files	Coverage Δ
...indings.Https/Stack/Https/HttpsTransportChannel.cs	68.45% <100.00%> (+0.64%)	⬆️
...ndings.Https/Stack/Https/HttpsTransportListener.cs	66.86% <100.00%> (+0.19%)	⬆️
...braries/Opc.Ua.Server/Subscription/Subscription.cs	59.06% <0.00%> (-0.56%)	⬇️
...raries/Opc.Ua.Server/Subscription/MonitoredItem.cs	44.02% <0.00%> (-0.31%)	⬇️
Libraries/Opc.Ua.Client/Session.cs	61.97% <0.00%> (-0.11%)	⬇️
Libraries/Opc.Ua.Client/Subscription.cs	70.90% <0.00%> (+0.48%)	⬆️

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