Also migrate from netstandard2.0 to netstandard2.1
Update following
Microsoft.Extensions.* from 3.1.21 to 6.0.0 (these were held back by net5.0 not being supported)
Microsoft.NET.Sdk.Functions from 3.0.13 to 4.0.1 (net 6.0)
Microsoft.ApplicationInsights from 2.18.0 to 2.20.0
Microsoft.CodeAnalysis.NetAnalyzers from 5.0.3 to 6.0.0
Microsoft.Azure.WebJobs.Extensions.DurableTask from 2.6.0 to 2.6.1
coverlet.collector 3.1.0 to 3.1.2
NUnit3TestAdapter to 4.1.0 to 4.2.1
nsubstitute 4.2.2 to 4.3.0
RestSharp 106.13.0 to 107.3.0
Use mcr.microsoft.com/dotnet/sdk:6.0-alpine instead of ptcos/multi-netcore-sdk:0.0.2, because features provided by multi-netcore-sdk are no longer necessary.