Rainforests calibration: separate models for each lead time and fixed thresholds

[btrotta-bom]

This needs to be reviewed by BoM first. I will add the "MO review required" tag after that has happened.

This PR makes 2 changes to the rainforests calibration code:

• Code now expects a set of models with different models for each lead time and threshold
• Instead of predicting the probability that the forecast error (i.e. observation minus forecast) exceeds a threshold, the models are now expected to predict the probability that the rainfall exceeds a threshold.

Testing:

• [X] Ran tests and they passed OK
• [X] Added new tests for the new feature(s)
• [X] Updated acceptance tests.

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (7e2ed68) 98.39% compared to head (4da70df) 98.39%. Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1940 +/- ## ======================================= Coverage 98.39% 98.39% ======================================= Files 123 123 Lines 11808 11817 +9 ======================================= + Hits 11618 11627 +9 Misses 190 190 ``` | [Files](https://app.codecov.io/gh/metoppv/improver/pull/1940?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=metoppv) | Coverage Δ | | |---|---|---| | [improver/calibration/rainforest\_calibration.py](https://app.codecov.io/gh/metoppv/improver/pull/1940?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=metoppv#diff-aW1wcm92ZXIvY2FsaWJyYXRpb24vcmFpbmZvcmVzdF9jYWxpYnJhdGlvbi5weQ==) | `99.46% <100.00%> (+0.07%)` | :arrow_up: | | [improver/ensemble\_copula\_coupling/constants.py](https://app.codecov.io/gh/metoppv/improver/pull/1940?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=metoppv#diff-aW1wcm92ZXIvZW5zZW1ibGVfY29wdWxhX2NvdXBsaW5nL2NvbnN0YW50cy5weQ==) | `100.00% <ø> (ø)` | | | [improver/ensemble\_copula\_coupling/utilities.py](https://app.codecov.io/gh/metoppv/improver/pull/1940?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=metoppv#diff-aW1wcm92ZXIvZW5zZW1ibGVfY29wdWxhX2NvdXBsaW5nL3V0aWxpdGllcy5weQ==) | `100.00% <ø> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/metoppv/improver/pull/1940/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=metoppv)

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[benowen-bom]

Thanks for making those updates. I think this is basically there, though there are just a few follow-up items I would like addressed before approving, but these are relatively small.

One other thing is that a couple of the acceptance tests are now failing following the updates. The issue is to do with the ['mosg__forecast_run_duration', 'mosg__model_configuratio'] attributes which are likely coming from the update to how the output cube is now created.

For some reason the comments in the review didn't carry over, so I'll add them again, but directly rather than bundled under a review.