Adds [minuteStep]="5" so the up/down arrows on the shared time picker step in five-minute increments, and rounds the emitted value to the nearest multiple of 5 in onModelChange. Non-aligned starting values (e.g. 14:23 picked up from current wall-clock or legacy data) snap onto the grid the first time the picker is interacted with, rather than incrementing forever off-grid.
Affects Start Time and End Time on social/group event editing, and Start Time, Meeting Time and Estimated Finish Time on walk editing, all of which share projects/ngx-ramblers/src/app/date-and-time/time-picker.ts.