Fix name resolution from a project's Main.qs

[swernli]

This fixes an issue where items from the Main.qs in a project would not be visible with the explicit Main namespace. When the dependency has no alias we should skip the special handling that elides the Main so that items are accessible as expected (and as documented in Running the Programs)

Fixes #2207

[minestarks]

The name resolution behavior table of doom:

Caller	Python interop	Code in same package / Entry expr in same package	Code in notebook cell / Entry expr from interpreter commands / Some code lens actions	Code in dependent package	Code in dependent package (stdlib special case)
Item visibility	all items	all items	all items	only exports	only exports
Main namespace treatment	Main exists	Main exists	Main exists	Main is collapsed	N/A, no Main in stdlib
Package alias?	No	No	No	Yes	No
Calling code lives in same or separate HIR package?	N/A, no code	Same	Separate	Separate	Separate

[DmitryVasilevsky]

The name resolution behavior table of doom:

@minestarks, Do we have this in the wiki or in the code? Could be useful...