perf: bool() elements of dirstate.status return instead of len()
I'm about to make scmutil.status no longer have a len(), so we need to do
something else to "use" the results in this perf method.
Differential Revision: https://phab.mercurial-scm.org/D7405
tags: use field names instead of field numbers on scmutil.status
As part of my pytype adventures I want to make scmutil.status no longer a
subclass of tuple. This is part of that process.
Differential Revision: https://phab.mercurial-scm.org/D7404