DLS internal errors when template declared inside composite object

[JonatanWaern]

Reproduces as

group g {
    template t {}
}

Will give
'''
Internal Error: Wanted to find context Template(SimpleSymbol { name: "t", loc: Span { ... } }, kind: Template }) in DMLCompositeObject { ... } which is not a known template object

Likely we should either
- Not internal error here
- Evaluate templates in invalid scopes as if they were declared at top level (I am partial to this, less breakage while editing)

[JonatanWaern]

Fixed by #206