Refactored ReflectorHost to allow it to be tested.
Fixed an issue where the .d.ts was findable but it wasn't used by the project
(This happens when the .metadata.json file references a module that was not
needed, such as it doesn't declare any types, and the reference to it was
elided by TypeScript when writing the .d.ts file).
Added tests for ReflectorHost
StaticReflector provides more context on errors reported by the
collector.
The metadata collector now records the line and character of the node that
caused it to report the error.
Includes other minor fixes to error reporting and a wording change.
Fixes#8978Closes#9011