- #5313
Also:
- preserve existing `TagHelperAttribute.ValueStyle`
- fix this in `UrlResolutionTagHelper`, `LinkTagHelper`, and `ScriptTagHelper` as well
- correct handling of non-`string` `classAttribute.Value`s in `TagHelperOutputExtensions`
- relates to #3918 because new `ClassAttributeHtmlContent` is smaller than any concatenated attribute value
nit: clean up `CacheTagHelper` whitespace and `using`s