go schemabuilder: Inline TextMarshaler/TextUnmarshaler types
go schemabuilder: Inline TextMarshaler/TextUnmarshaler types

Summary: Preloads the TextMarshaler and TextUnmarshaler reflect types so
we can assert whether types implement one or the other.

samsarahq/thunder,samsarahq/thunder,samsarahq/thunder,samsarahq/thunder,samsarahq/thunder