change `data` to `forecast` in `score()` and update related tests

[nikosbosse]

Description

This PR closes #.

• Changed the argument from data to forecast in the following functions
  • score()
  • validate_forecast() (but not validate_general())
  • get_forecast_counts()
  • get_pit()
  • sample_to_quantile()
  • interval_long_to_quantile()
  • quantile_to_interval()
  • transform_forecasts()
• updated tests where necessary

The validate_general() is a bit of an edge case. Context:

• the function does all the validations that are the same for the different validate_forecast() methods
• It is exported for two reasons:
  • it's an S3 method and I only recently learned you could have them be internal
  • it could be useful for people who want to create their own classes and run their own checks

Since the function doesn't require a forecast object (although it requires a data.table I'm leaning towards calling the first arg data instead of forecast. This would be analogously to e.g. as_forecast() or get_forecast_unit(), which also don't require a forecast object.

Checklist

• [x] My PR is based on a package issue and I have explicitly linked it.
• [x] I have included the target issue or issues in the PR title as follows: issue-number: PR title
• [x] I have tested my changes locally.
• [x] I have added or updated unit tests where necessary.
• [x] I have updated the documentation if required.
• [x] I have built the package locally and run rebuilt docs using roxygen2.
• [x] My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• [ ] I have added a news item linked to this PR.
• [ ] I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.31%. Comparing base (b56cf28) to head (fa538c7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #772 +/- ## ========================================== + Coverage 95.30% 95.31% +0.01% ========================================== Files 21 21 Lines 1598 1602 +4 ========================================== + Hits 1523 1527 +4 Misses 75 75 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[nikosbosse]

I like the idea. validate_forecast_all()?

[nikosbosse]

New issue for this discussion: https://github.com/epiforecasts/scoringutils/issues/773