refactor(predicates): return features instead of bool, add P00/P11 predicates

- Change predicate return type from `bool` to `features list option` to
  carry extracted event data (Summary, Day_start, Multi_day) alongside
  match results
- Add `features` type with Generic_feature_presence, Summary, Day_start,
  Multi_day variants
- Add P00 (has_summary) and P11 (override_events) predicates
- Remove large commented-out icalendar/ptime type definitions
- Refactor main.ml to group events by UID using a Map
- Add get_y_m_d_from_timedesc helper to Utils

bin/utils.ml

@@ -24,6 +24,10 @@ let timedesc_of_date_or_datetime (t : date_or_datetime) : Timedesc.t =
   | `Date (year, month, day) ->
     Timedesc.make_exn ~year ~month ~day ~hour:0 ~minute:0 ~second:0 ~tz:(Timedesc.Time_zone.local_exn ()) ()
 
+let get_y_m_d_from_timedesc (t : Timedesc.t) : int * int * int =
+  let date = Timedesc.date t in
+  (Timedesc.Date.year date, Timedesc.Date.month date, Timedesc.Date.day date)
+
 let get_start ev =
   let _, start = ev.dtstart in
   timedesc_of_date_or_datetime start