Fix string truncation calls all over the codebase.

Summary: Fixes T6608, though I'll also clean up the comment for PhutilStringTruncator in another diff. If I understand correctly, before T1191, MySQL column length was by character count and post T1191 its by byte count. Ergo, most of these changes are going from codepoint -> bytes. See test plan for complete list of what was and was not done.

Test Plan:
Thought very carefully about each callsite and made changes as appropos. "Display" means the string is clearly used for display-only purposes and correctly uses "glyph" already.

grep -rn PhutilUTF8StringTruncator *

applications/calendar/query/PhabricatorCalendarEventSearchEngine.php:217: ->addAttribute(id(new PhutilUTF8StringTruncator()) -- display
applications/chatlog/controller/PhabricatorChatLogChannelLogController.php:111: $author = id(new PhutilUTF8StringTruncator()) -- display
applications/conduit/method/ConduitConnectConduitAPIMethod.php:62: $client_description = id(new PhutilUTF8StringTruncator()) -- was codepoint, changed to bytes
applications/conpherence/view/ConpherenceFileWidgetView.php:22: ->setFileName(id(new PhutilUTF8StringTruncator()) -- display
applications/differential/controller/DifferentialDiffViewController.php:65: id(new PhutilUTF8StringTruncator()) -- display
applications/differential/event/DifferentialHovercardEventListener.php:69: id(new PhutilUTF8StringTruncator()) -- display
applications/differential/parser/DifferentialCommitMessageParser.php:144: $short = id(new PhutilUTF8StringTruncator()) -- was glyphs, made to bytes
applications/differential/view/DifferentialLocalCommitsView.php:80: $summary = id(new PhutilUTF8StringTruncator()) -- display
applications/diffusion/controller/DiffusionBrowseFileController.php:686: id(new PhutilUTF8StringTruncator()) -- display
applications/feed/story/PhabricatorFeedStory.php:392: $text = id(new PhutilUTF8StringTruncator()) -- display, unless people are saving the results of renderSummary() somewhere...
applications/harbormaster/storage/build/HarbormasterBuild.php:216: $log_source = id(new PhutilUTF8StringTruncator()) -- was codepoints now bytes
applications/herald/storage/transcript/HeraldObjectTranscript.php:55: // NOTE: PhutilUTF8StringTruncator has huge runtime for giant strings. -- not applicable
applications/maniphest/export/ManiphestExcelDefaultFormat.php:107: id(new PhutilUTF8StringTruncator()) -- bytes
applications/metamta/storage/PhabricatorMetaMTAMail.php:587: $body = id(new PhutilUTF8StringTruncator()) -- bytes
applications/people/event/PhabricatorPeopleHovercardEventListener.php:62: id(new PhutilUTF8StringTruncator()) -- display
applications/phame/conduit/PhameCreatePostConduitAPIMethod.php:93: id(new PhutilUTF8StringTruncator()) -- was codepoints, now bytes
applications/pholio/storage/PholioTransaction.php:300: id(new PhutilUTF8StringTruncator()) -- display
applications/phortune/provider/PhortuneBalancedPaymentProvider.php:147: $charge_as = id(new PhutilUTF8StringTruncator()) -- bytes
applications/ponder/storage/PonderAnswerTransaction.php:86: id(new PhutilUTF8StringTruncator()) -- display
applications/ponder/storage/PonderQuestionTransaction.php:267: id(new PhutilUTF8StringTruncator()) -- display
applications/ponder/storage/PonderQuestionTransaction.php:276: id(new PhutilUTF8StringTruncator()) -- display
applications/repository/storage/PhabricatorRepositoryCommitData.php:43: $summary = id(new PhutilUTF8StringTruncator()) -- was codepoints, now bytes
applications/repository/worker/commitmessageparser/PhabricatorRepositoryCommitMessageParserWorker.php:20: $data->setAuthorName(id(new PhutilUTF8StringTruncator()) -- was codepoints, now bytes
applications/slowvote/query/PhabricatorSlowvoteSearchEngine.php:158: $item->addAttribute(id(new PhutilUTF8StringTruncator()) -- display
infrastructure/daemon/workers/query/PhabricatorWorkerLeaseQuery.php:317: $host = id(new PhutilUTF8StringTruncator()) -- bytes
view/form/control/AphrontFormPolicyControl.php:61: $policy_short_name = id(new PhutilUTF8StringTruncator()) -- glyphs, probably display only

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6608

Differential Revision: https://secure.phabricator.com/D11219