- #3571 and part of #3123
- split `ContentViewComponentResult` in two
- add `HtmlEncoder` to `ViewComponentContext`
- remove use of `WebUtility.HtmlEncode()` and `HtmlDecode()`
nits: remove unused `using`s in files I had open
Abstractions - Core MVC extensibility
Controllers - MVC implementations of .Abstractions and supporting
contracts
Infrastructure - General purpose support APIs. Metadata APIs that don't
fit clearly with a feature or with .Abstraction