Add Kalman Filter, Input and Measurement builders

[sunsided]

This adds builders to quickly conjure a filter when the alloc crate feature is enabled. This turns the lengthy buffer wiring into a simple

let builder = KalmanFilterBuilder::<NUM_STATES, f32>::default();
let mut filter = builder.build();
let mut input = builder.inputs().build::<NUM_INPUTS>();
let mut measurement = builder.measurements().build::<NUM_MEASUREMENTS>();

These returned types still require the temporary buffers. While this works for this specific crate, it would be nice if we could just keep it to the strictly necessary definitions (i.e., no temp buffers in the type signature).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.61621% with 20 lines in your changes missing coverage. Please review.

Project coverage is 81.80%. Comparing base (af24668) to head (5a366d1).

Files	Patch %	Lines
crates/minikalman/src/test_dummies.rs	0.00%	20 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12 +/- ## =========================================== + Coverage 44.77% 81.80% +37.03% =========================================== Files 28 30 +2 Lines 2890 3897 +1007 =========================================== + Hits 1294 3188 +1894 + Misses 1596 709 -887 ```

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