Make `arc tasks` print output in a unicode-aware and console-width-aware way
Make `arc tasks` print output in a unicode-aware and console-width-aware way

Summary:
Currently, we print `arc tasks` in a console-agnostic and unicode-unaware way, so:

  - Tasks with multibyte characters get aligned incorrectly (see T1831); and
  - narrow terminals plus long task names results in a broken display.

Test Plan: Ran `arc tasks`. Will post screenshots.

Reviewers: btrahan, vrana, Korvin

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T749, T1831

Differential Revision: https://secure.phabricator.com/D3568

KieranHayes/arcanist,phacility/arcanist,coursera/arcanist,fivestars/arcanist,chundongwang/arcanist,eSpark/arcanist,coursera/arcanist,folsom-labs/arcanist,Khan/arcanist,hach-que/arcanist,codelabs-ch/arcanist,calblueprint/arcanist,julkiewicz/arcanist,uber/arcanist,aik099/arcanist,phacility/arcanist,zhihu/arcanist,alexmv/arcanist,Khan/arcanist,Symplicity/arcanist,haskell-infra/arcanist,PageUpPeopleOrg/arcanist-patches,wharris/arcanist,fivestars/arcanist,jra3/arcanist,kevinseelbach/arcanist,KieranHayes/arcanist,wxstars/arcanist,wxstars/arcanist,eSpark/arcanist,alexmv/arcanist,calblueprint/arcanist,uber/arcanist,haskell-infra/arcanist,PageUpPeopleOrg/arcanist-patches,wharris/arcanist,memsql/arcanist,eSpark/arcanist,alexmv/arcanist,phacility/arcanist,memsql/arcanist,wharris/arcanist,julkiewicz/arcanist,zhihu/arcanist,sneakpeeq/arcanist,r4nt/arcanist,PageUpPeopleOrg/arcanist-patches,Symplicity/arcanist,hach-que/arcanist,julkiewicz/arcanist,wikimedia/phabricator-arcanist,Symplicity/arcanist,Symplicity/arcanist,jra3/arcanist,wxstars/arcanist,haskell-infra/arcanist,zhihu/arcanist,r4nt/arcanist,KieranHayes/arcanist,fivestars/arcanist,zhihu/arcanist,uber/arcanist,wikimedia/phabricator-arcanist,julkiewicz/arcanist,chundongwang/arcanist,Khan/arcanist,hach-que/arcanist,wikimedia/phabricator-arcanist,phacility/arcanist,kevinseelbach/arcanist,aik099/arcanist,haskell-infra/arcanist,r4nt/arcanist,phacility/arcanist,memsql/arcanist,hach-que/arcanist,sneakpeeq/arcanist,kevinseelbach/arcanist,PageUpPeopleOrg/arcanist-patches,coursera/arcanist,uber/arcanist,dguo-coursera/arcanist,folsom-labs/arcanist,dguo-coursera/arcanist,sneakpeeq/arcanist,folsom-labs/arcanist,dguo-coursera/arcanist,codelabs-ch/arcanist,kevinseelbach/arcanist,wikimedia/phabricator-arcanist,fivestars/arcanist,codelabs-ch/arcanist,wharris/arcanist,chundongwang/arcanist,codelabs-ch/arcanist,jra3/arcanist,wxstars/arcanist,sneakpeeq/arcanist,chundongwang/arcanist,eSpark/arcanist,aik099/arcanist,codelabs-ch/arcanist,dguo-coursera/arcanist,r4nt/arcanist,alexmv/arcanist,calblueprint/arcanist,memsql/arcanist,KieranHayes/arcanist,calblueprint/arcanist,jra3/arcanist,folsom-labs/arcanist,coursera/arcanist,Khan/arcanist,aik099/arcanist