Commit 2021-04-21 04:20 923314f2

refactor(order/well_founded_set): partially well ordered sets using relations other than has_le.le (#7131) Introduces set.partially_well_ordered_on to generalize set.is_partially_well_ordered to relations that do not necessarily come from a has_le instance Renames set.is_partially_well_ordered to set.is_pwo in analogy with set.is_wf Prepares to refactor Hahn series to use set.is_pwo and avoid the assumption of a linear order