Add a Rust implementation for 1d Gaussian exponential family state nodes

[LegrandNico]

This PR introduced the first re-implementation of the framework in Rust, focusing on generalized filtering for now.

[codecov-commenter]

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Codecov Report

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

Project coverage is 95.39%. Comparing base (493d226) to head (c84ed0f).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #229 +/- ## ======================================= Coverage 95.39% 95.39% ======================================= Files 22 22 Lines 1130 1130 ======================================= Hits 1078 1078 Misses 52 52 ```

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