phabricator: refactor `phabread` to write all patches at once This will be necessary to create a first class `phabimport` command. That command requires a transaction, and will import all named patches within a single transaction. But if Phabricator queries also happen within the transaction, that leaves open the chance that an exception is raised, the transaction is abandoned, and the next command that is run will complain about needing to run `hg recover`. Differential Revision: https://phab.mercurial-scm.org/D8135

phabricator: make `hg phabupdate` work outside of a repository This is similar to 16312ea45a8b- we don't need a repo, but will load .hg/hgrc if inside one. Differential Revision: https://phab.mercurial-scm.org/D8208

phabricator: pass ui instead of repo to `userphids()` Also not a repository operation. Differential Revision: https://phab.mercurial-scm.org/D8207