Changes:
* Stop producing Microsoft.AspNetCore.Routing.DecisionTree.Sources. I could not find any usages outside of the Microsoft.AspNetCore.Routing assembly, so I've moved this to be a subfolder of code in the Microsoft.AspNetCore.Routing project.
* Stop building src/Routing as a submodule. Use ProjectReference instead
* Move projects from src/Routing into src/Http/Routing/ and src/Http/Routing.Abstractions/
* Update package baselines and dependencies to support building routing projects and samples
* Replace the aspnet/JsonPatch git submodule and merge the master branch of its source to this repo
* Likewise for aspnet/DotNetTools
* And aspnet/HtmlAbstractions
* merge latest infrastructure changes from the release/2.2 branch