[Autofill] Move RationalizeAndAssignSections() out of DetermineHeuristicTypes()

This CL moves RationalizeAndAssignSections() out of
DetermineHeuristicTypes() and adds the necessary calls of
RationalizeAndAssignSections().

The motivation for this change is that DetermineHeuristicTypes()
will become a free function and operate on FormData instead of
FormStructure.
RationalizeAndAssignSections() will remain a member function of
FormStructure because it needs access to several members of
AutofillField. RationalizeAndAssignSections() is relatively cheap
and is called on the UI thread in OnLoadedServerPredictions()
already.

The CL was produced by joining lines of DetermineHeuristicTypes()
calls and then applying the following substitution:

%s/\(\s*\)\(\S*\(->\|\.\)\)DetermineHeuristicTypes(\(\S\+\), \(\S\+\), \(\S\+\));/\0\r\1\2RationalizeAndAssignSections(\4, \5, \6);

Bug: 427787155, 40232021
Change-Id: I4c0f1a167f0795b044811c7b9e04515205a1a88b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6902838
Commit-Queue: Christoph Schwering <schwering@google.com>
Reviewed-by: Jan Keitel <jkeitel@google.com>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1509491}