mathlib3

31800d81 - refactor(topology/constructions): review `quotient` API (#15986)

refactor(topology/constructions): review `quotient` API (#15986) * rename `continuous_quotient_lift` to `continuous.quotient_lift`; * rename `continuous_quotient_lift_on'` to `continuous.quotient_lift_on'`; * add `continuous.quotient_map'` and use it to golf some proofs.