refactor: Rename *_for_at_mentioning functions.
refactor: Rename *_for_at_mentioning functions.

This name was misleading, since this code is used
in sort_recipients, which happens when you, for
example, autocomplete persons in the "To:" box
when composing (and has nothing to do with
mentioning).

kou/zulip,punchagan/zulip,eeshangarg/zulip,timabbott/zulip,hackerkid/zulip,andersk/zulip,punchagan/zulip,kou/zulip,punchagan/zulip,timabbott/zulip,shubhamdhama/zulip,zulip/zulip,shubhamdhama/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,kou/zulip,timabbott/zulip,showell/zulip,rht/zulip,kou/zulip,synicalsyntax/zulip,synicalsyntax/zulip,kou/zulip,hackerkid/zulip,shubhamdhama/zulip,brainwane/zulip,shubhamdhama/zulip,punchagan/zulip,brainwane/zulip,zulip/zulip,brainwane/zulip,eeshangarg/zulip,andersk/zulip,brainwane/zulip,andersk/zulip,andersk/zulip,punchagan/zulip,showell/zulip,rht/zulip,eeshangarg/zulip,showell/zulip,rht/zulip,rht/zulip,zulip/zulip,zulip/zulip,synicalsyntax/zulip,hackerkid/zulip,showell/zulip,brainwane/zulip,showell/zulip,brainwane/zulip,timabbott/zulip,shubhamdhama/zulip,brainwane/zulip,synicalsyntax/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,shubhamdhama/zulip,timabbott/zulip,synicalsyntax/zulip,hackerkid/zulip,eeshangarg/zulip,punchagan/zulip,shubhamdhama/zulip,hackerkid/zulip,punchagan/zulip,andersk/zulip,timabbott/zulip,hackerkid/zulip,rht/zulip,synicalsyntax/zulip,zulip/zulip,zulip/zulip,kou/zulip,zulip/zulip,rht/zulip,showell/zulip,synicalsyntax/zulip,andersk/zulip,showell/zulip,timabbott/zulip,hackerkid/zulip