Add raw CRS string as an eo3 search field

[jeremyh]

As requested in #280

Example of updating my local (NCI-clone) datacube:

❯ datacube -v metadata update digitalearthau/config/eo3/eo3*.odc-type.yaml  
2021-03-03 17:03:33,217 13549 datacube INFO Running datacube command: /home/jez/dea/venv/bin/datacube -v metadata update eo3_landsat_ard.odc-type.yaml eo3_landsat_l1.odc-type.yaml eo3.odc-type.yaml
2021-03-03 17:03:33,271 13549 datacube.index._metadata_types INFO Safe change in dataset.search_fields.crs_raw from missing to {'description': 'The raw CRS string as appears in metadata', 'offset': ['crs'], 'indexed': False}
2021-03-03 17:03:33,271 13549 datacube.index._metadata_types INFO Updating metadata type eo3_landsat_ard
Updated "eo3_landsat_ard"
2021-03-03 17:03:33,443 13549 datacube.index._metadata_types INFO Safe change in dataset.search_fields.crs_raw from missing to {'description': 'The raw CRS string as appears in metadata', 'offset': ['crs'], 'indexed': False}
2021-03-03 17:03:33,443 13549 datacube.index._metadata_types INFO Updating metadata type eo3_landsat_l1
Updated "eo3_landsat_l1"
2021-03-03 17:03:33,590 13549 datacube.index._metadata_types INFO Safe change in dataset.search_fields.crs_raw from missing to {'description': 'The raw CRS string as appears in metadata', 'offset': ['crs'], 'indexed': False}
2021-03-03 17:03:33,590 13549 datacube.index._metadata_types INFO Updating metadata type eo3
Updated "eo3"

• ~Keeping as draft as I want to confirm a search locally, tomorrow morning, before merging~.
• I set indexed: false as I believe this will always be used with other, stronger query arguments.

[codecov[bot]]

Codecov Report

Merging #281 (01f637d) into develop (cc02071) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #281   +/-   ##
========================================
  Coverage    67.10%   67.10%           
========================================
  Files           42       42           
  Lines         3219     3219           
========================================
  Hits          2160     2160           
  Misses        1059     1059           

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update cc02071...01f637d. Read the comment docs.