Update DEA Intertidal to use eo-tides

[robbibt]

Updates repo to use eo-tides instead of DEA Tools:

• Updated Python packaging to use eo-tides
• Switched to eo-tides version of pixel_tides function
• Switched default model to EOT20 (instead of FES2014) to match eo-tides default
• Updated documentation and removed some outdated/unused code (e.g. export_intertidal_rasters, tidal_offset_tidelines, pixel_ebb_flow)

Annoyingly I have commited some extra code I was working on a while ago, to add spearman correlation as an alternative tide correlation method (it should have been in a different PR to keep this one easier to review!). It's mainly in the spearman_correlation and a little bit in ds_to_flat.

[github-actions]

For full integration test results, refer to the Tests directory README.

[vnewey]

Nice work Robbi.

[erialC-P]

I haven't loaded and run the code but it all looks good in the github codespace!