new glm_predictive_distribution and corresponding changes in LaplaceRedux.predict

[pasq-cat]

this pull request add the following things:

• add a function that check if a finaliser layer has already been added to the model
• change the glm_predictive_distribution so that it also return a distribution object
• change predict so that it can also return distributions
• add unit tests for the new functions -part of the gsoc (2024)

[pasq-cat]

@pat-alt brah! what happened? i only changed a number!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.27%. Comparing base (3e1531d) to head (b59fc14).

Files	Patch %	Lines
src/baselaplace/predicting.jl	96.87%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #99 +/- ## ========================================== + Coverage 94.95% 95.27% +0.32% ========================================== Files 21 21 Lines 575 593 +18 ========================================== + Hits 546 565 +19 + Misses 29 28 -1 ```

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[pasq-cat]

@pat-alt @MojiFarmanbar i tried to cover all the new cases but since there are a lot of ifs i had to add multiple tests.

[pat-alt]

@MojiFarmanbar do you want to have a quick look as well or should we merge this?

[MojiFarmanbar]

@pat-alt i had a quick look, if you approve it then i would say let's merge it.