Account for lineage location in postgis datasets

[Ariana-B]

Reason for this pull request

SimpleDocNav assumes document lineage will have been rewritten to be at ('lineage', 'source_datasets'), which doesn't happen in the postgis driver, causing lineage information to not be captured correctly.

Proposed changes

• Have SimpleDocNav check if there is lineage information present at ('lineage') if there is nothing at ('lineage', 'source_datasets')

• Closes #xxxx

• Tests added / passed

• Fully documented, including docs/about/whats_new.rst for all changes

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📚 Documentation preview 📚: https://datacube-core--1687.org.readthedocs.build/en/1687/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.61%. Comparing base (8f3e5a9) to head (554a987).
Report is 2 commits behind head on develop-1.9.

Additional details and impacted files

@@             Coverage Diff              @@
##           develop-1.9    #1687   +/-   ##
============================================
  Coverage        85.61%   85.61%           
============================================
  Files              151      151           
  Lines            15528    15526    -2     
============================================
- Hits             13294    13293    -1     
+ Misses            2234     2233    -1     

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[SpacemanPaul]

LGTM, good catch