Remove support for multiple locations from postgis index

[Ariana-B]

Reason for this pull request

Rather than simply deprecating, remove multiple location support entirely from the postgis index. Related deprecated methods are either no-ops or only work with a single location.
Also remove unnecessary and unused code previously copied over from eo-datasets (no impact).

Proposed changes

• Delete DatasetLocation table and integrate uri data into the Dataset table

• Error if attempting to add or update a dataset with multiple locations

• Alter deprecated location methods to only work with one location

• Closes #xxxx

• Tests added / passed

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

---

📚 Documentation preview 📚: https://datacube-core--1658.org.readthedocs.build/en/1658/

[SpacemanPaul]

Looks good, but let's make the migration a proper migration.

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 20 lines in your changes missing coverage. Please review.

Project coverage is 85.56%. Comparing base (015ddae) to head (a01d968).
Report is 11 commits behind head on develop-1.9.

Files with missing lines	Patch %	Lines
...sions/d27eed82e1f6_remove_datasetlocation_table.py	53.84%	12 Missing ⚠️
datacube/index/postgis/_datasets.py	80.00%	6 Missing ⚠️
datacube/drivers/postgis/_api.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           develop-1.9    #1658      +/-   ##
===============================================
+ Coverage        85.22%   85.56%   +0.34%     
===============================================
  Files              144      143       -1     
  Lines            15787    15418     -369     
===============================================
- Hits             13454    13192     -262     
+ Misses            2333     2226     -107     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests

[SpacemanPaul]

Approved, once mypy and precommit checks pass.