[NFC] Take custom comparator in TopologicalSort::minSort (#6890)

Rather than finding the minimum sort with respect to the original order
of vertices, find the minimum sort with respect to an arbitrary
user-provided comparator. Users of the minSort utility previously had to
sort their input graphs according to their desired ordering, but now
they can simply provide their comparator instead.

Take advantage of the new functionality in ReorderGlobals and also
standardize on a single data type for representing dependence graphs to
avoid unnecessary conversions. Together, these changes slightly speed up
ReorderGlobals.

Move the topological sort code previously in a .cpp file into the header
so the comparator can be provided as a lambda template parameter instead
of as a `std::function`. This makes ReorderGlobals about 5% faster.

0 files changed, 0 insertions, 0 deletions