Port pulses to use entities

frontend/src/metabase/lib/entities.js

frontend/src/metabase/pulse/actions.js

frontend/src/metabase/pulse/components/PulseEdit.jsx

frontend/src/metabase/pulse/components/PulseEditCards.jsx

frontend/src/metabase/pulse/components/PulseEditChannels.jsx

frontend/src/metabase/pulse/components/RecipientPicker.jsx

frontend/src/metabase/pulse/containers/PulseEditApp.jsx

frontend/src/metabase/pulse/reducers.js

frontend/src/metabase/pulse/selectors.js

...end/src/metabase/query_builder/components/AlertModals.jsx

frontend/test/alert/alert.integ.spec.js

frontend/test/pulse/pulse.integ.spec.js