Enable trimming/AOTing in consuming applications

[baronfel]

Is your feature request related to a problem? Please describe.

We need to be able to enable consumers of the template engine to use trimmed/AOT modalities, so we need to be trimming compatible.

Describe the solution you'd like.

We need to enable IsTrimCompatible, and then systematically address sources of trim-incompatibility in the codebase. Proof positive would be to have a trimmed or AOT test app that exercises the library in-tree. It's possible that this mode would require a new TFM to the libraries.

There are going to be some very rough areas. Json serialization is easy enough, but the core of the template engine is a reflection-based, delay-loaded, wild-west component system.

Additional context

No response