Include route information when user hovers on the generated doc

[RodgeFu]

Clear and concise description of the problem

When user hovers on some element in the generated doc, he can see the route information about how the element is generated from typespec.

We would need compiler and emitter support to provide the route information to show in ide. @allenjzhang will provide more detail about this feature and design.

Checklist

• Follow our Code of Conduct
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[timotheeguerin]

Duo of #1993
This needs design in the compiler library api