fix shifted events when dealing with different Time zones
Since new libEcal, iCal TZID field can be stored as city. our current code does not recognize it, and fallback to UTC making events shifted according to user's timezone.
The idea is to provide a Map of city name -> iana record. Also make the tezone search more robust to different situations.
fix ubports/development/apps/lomiri-calendar-app#228 (closed)
test: sudo ubports-qa install focal_-_PR_qtorganizer5-eds_18
Note that in calendar app, in Day view, the event may not appear ( still shown in week, month and calendar views). A work around is doable for that in calendar app, will be done in another MR
Edited by Lionel Duboeuf