minor: Tweak build_person_matcher.
minor: Tweak build_person_matcher.

This is not a major speedup, but we do a couple
simple things here:

    - trim the query outside the function we
      build (that might be called multiple times)

    - don't split names before we possibly
      early-exit with an email match

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