Investigate d.ts exports map

I don’t quite understand the expected behavior here or what’s being shown. nominal.ts exports a type that uses a global type declared in types.d.ts. A change to types.d.ts could cause a change to any file importing nominal.ts.

_Originally posted by @andrewbranch in https://github.com/microsoft/TypeScript/pull/48616#discussion_r850866269_
