v1.11.0 - change Link timezones from hard links to symbolic links

• 1.11.0 (2022-02-14, TZDB 2021e)
  • Regenerate zonedb/ and zonedbx/ using latest AceTimeTool which
    identifies notable Zones and Policies whose DST shifts are not exactly
    0:00 or 1:00. No actual data change. Notable policies relevant from 2000
    until 2050 are:
    • ZonePolicy Eire: DST shift -1:00
    • ZonePolicy LH: DST shift 0:30
    • ZonePolicy Morocco: DST shift -1:00
    • ZonePolicy Namibia: DST shift -1:00
    • ZonePolicy StJohns: DST shift 2:00
    • ZonePolicy Troll: DST shift 2:00
  • Add support for overflow and underflow to TimePeriod.
    • When isError() returns true, the sign() method discriminates
      3 error conditions, and the printTo() prints the following:
      • 0: generic error, ""
      • +1: overflow, "<+Inf>"
      • -1: underflow, "<-Inf>"
      • See USER_GUIDE.md#TimePeriod.
  • Change Link entries from "hard links" to "symbolic links".
    • This allows a TimeZone object to know whether it is a Zone entry
      or a Link entry.
    • Add TimeZone::isLink() and ZoneProcessor::isLink() methods.
    • Add bool followLink = true parameter to various other methods
      (getZoneId(), printTo(), printShortTo()) which determines
      whether the method resolves to the current Link entry or follows the
      link to the destination Zone entry.
    • MemoryBenchmark says that this increases
      flash consumption by 100-300 bytes, due to the extra code needed to
      follow the symlink. But the ability to determine whether the TimeZone
      is a link or not will be necessary for an upcoming feature, so this
      slight increase in flash consumption seems worth it.
    • Regenerate zonedb/ and zonedbx to convert Link entries from
      hard links to symbolic links.
    • See Symbolic Links for more info.
  • Add offset_date_time_mutation methods.
    • Similar to zoned_date_time_mutation methods.
    • Provides some convenient mutation methods for OffsetDateTime.
  • Upgrade Arduino CLI from 0.19.2 to 0.20.2.