fix: SSR templates rendered with the `useFASTStyle` has significant FOUSC

[nicholasrice]

🐛 Bug Report

I noticed when experimenting with SSR code that when using the FASTStyle component to reduce component stylesheet payload, there was a pretty significant FOUSC when loading the page.

I'm not 100% certain why so we'll need to some investigations. I thought that because the FASTStyle element was defined in the head, it would upgrade prior to painting the custom element's shadow DOM, but that did not seem to be the case.