176: Move completio to ra_analysis r=matklad a=matklad
While we should handle completion for isolated file, it's better
achieved by using empty Analysis, rather than working only with &File:
we need memoization for type inference even inside a single file.
Co-authored-by: Aleksey Kladov <aleksey.kladov@gmail.com>
This is a first step towards queryifing completion and resolve.
Some code currently duplicates ra_editor: the plan is to move all
completion from ra_editor, but it'll take more than one commit.
