[Autofill][Leipzig] Tests for getting/setting structured address tokens.

Adds test to check getting and setting the structured address tokens.
It is also tested that the tokens are reset if the unstructured
information changes.

Change-Id: Ia10d19bc31a11443beb31ee509b35a33b68edad6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2355904


Reviewed-by: Christoph Schwering <schwering@google.com>
Commit-Queue: Matthias Körber <koerber@google.com>
Cr-Commit-Position: refs/heads/master@{#798122}