Upgrade docfx to fix documentation

[WalkerCodeRanger]

The documentation is generated using a cake build script and docfx.console version 2.59.4. That NuGet package has been deprecated, and we are now supposed to use the docfx package. However, it seems to not be a drop in replacement. Switching to that package with the same version causes an exception in the build process.

There appear to be issues with the v3 docs that might be addressed by upgrading docfx. However, upgrading will take a while to figure out.

Resources:

• How to build DocFx site via Visual Studio/Azure DevOps/TFS

[WalkerCodeRanger]

As part of this, see if we can emit source links in the docs. If it isn't simple to do so, create a separate issue for that.