Net Core/Net 5 - Implementation #3197

Track the progress remaining on actually compiling the project with .Net Core

Basic support for compiling with .Net Core was added with #3181 with additional commit (e8cf336) to get the core projects compiling/tests passing,

• Integrate PDB into dll (bug in package reference makes it near impossible to distribute a pdb, see New project system doesn't copy PDBs from packages dotnet/sdk#1458)
• Integrate source code directly into the dll if the size doesn't increase dramatically see cefsharp/CefSharp.Wpf.HwndHost@901c6a7#diff-5418bd97c668e509388f5d466d94a436R10 for an example
• Generate reference assemblies for csproj
• Generate reference assembly for CefSharp.Core.dll using GenApi
• Improve Reference Assembly generation as relies on x64 hardcoded in project file. See Net Core/Net 5 - Implementation #3197 (comment)
• Check if we need to make the BrowserSubProcess TSAware (it's now a WinExe rather than a console exe so not sure that we have to).
• Add Net Core Unit Test Project
• Update appveyor to build the matrix (Net Core requires a VS2019 build worker image)
• Add assembly manifest for VC++ projects to prevent loading issues of ijwhost.dll see C++/CLI libraries may fail to load due to ijwhost.dll not being on the search path dotnet/runtime#38231 and Ijwhost.dll loading not always working for C++/CLI assembly. dotnet/runtime#37972 (comment)
• Distribute ijwhost.dll as required to load C++/CLI
• Dynamically set version number in chromiumembeddedframework.runtime.json
• Finish Nuget packages (partially done, they don't work yet)
• Fix type in .targets file as detailed in Net Core/Net 5 - Implementation #3197 (comment)
• Update Dependency Check (possibly create a Net Core variant).
• Update BrowserSubProcess to support running on .Net 5.0 when .Net Core is not installed.
• Add .Net Core specific Nuget Readme.txt
• VC++ 2019 is required for .Net Core (add to readme, document in other places).
• Confirm SelfPublish works after major changes in Refactor CefSharp.Core into CefSharp.Core.Runtime #3311
• SelfHost for Net Core determine CefSharp.BrowserSubprocess.Core.dll path based on .exe path (details in Net Core/Net 5 - Implementation #3197 (comment))

OffScreen

• Add dependency to https://www.nuget.org/packages/System.Drawing.Common/4.7.0 (as uses System.Drawing.Bitmap)