This commit defines the interfaces which outline the information the
`TemplateTypeChecker` can return when requesting a Symbol for an item in the
`TemplateAst`.
Rather than providing the `ts.Symbol`, `ts.Type`, etc.
information in several separate functions, the `TemplateTypeChecker` can
instead provide all the useful information it knows about a particular
node in the `TemplateAst` and allow the callers to determine what to do
with it.
PR Close#38618
9e77bd3087