search: facilitate simple searches if globbing is active
Created by: stefanhengl
Relates to https://github.com/sourcegraph/sourcegraph/issues/12476
With this PR we slightly modify the interpretation of filter values if globbing is active.
Users can now enter queries like
repo:sourcegraph file:search.go
which will be interpreted as
repo:**sourcegraph** file:**search.go**
in the backend.
Filter values containing glob symbols or path separators will be interpreted as glob-pattern without further modification. Results that match the file: filter value exactly (e.g. files named search.go in any directory) will be listed first. Multiple exact matches are sorted by length of the file path, and then alphabetically.