[Autofill] Add date parsing and formatting functions

This CL adds functions for formatting and parsing of dates (= year,
month, day tuples). Followup CLs use these functions for entities.

Bug: 396325496
Change-Id: Id4eaa58943d66ac0d39a0746d0f608879a5f8b0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6312740
Reviewed-by: Jan Keitel <jkeitel@google.com>
Commit-Queue: Christoph Schwering <schwering@google.com>
Cr-Commit-Position: refs/heads/main@{#1427143}