Change bin/sh to bin/bash in an obscure script

Summary: Packaging tools are tripping up on this since it has bashisms. Just
make it a bash script.

Auditors: btrahan
Fix a minor formatting issue in the service call log

Summary: There was already a "conduit" branch for real Conduit calls which I
missed. Reuse it for in-process service calls.

Auditors: btrahan
Mark build_xhpast.sh as a bash script, too

Summary: See previous similar commit.

Auditors: btrahan
Improve performacne of PhutilSymbolLoader

Summary: Currently, we build way more symbols than we need to when doing `loadObjects()`. Instead, select only the candidates we know will match the request.

Test Plan: 650ms -> 380ms on Differential revision page, which hits this more than it probably should.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7584