feat: add functions to extract multiple subsets at once.

[kyle-cochran]

Add
VectorXd State::extractCoordinates(const Array<Shared<const CoordinatesSubset>>& aCoordinatesSubsetsArray) const;

and

    VectorXd CoordinatesBroker::extractCoordinates(
        const VectorXd& aFullCoordinatesVector, const Array<Shared<const CoordinatesSubset>>& aCoordinatesSubsetsArray
    ) const;

to allow extracting multiple subsets at once.

This is a preliminary step for whatever State::contract/slice/etc. function we implement.

Also add doc-strings to the State class.

[codecov]

Codecov Report

Merging #234 (c1b6eaf) into main (4465595) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #234      +/-   ##
==========================================
+ Coverage   82.79%   82.84%   +0.04%     
==========================================
  Files          62       62              
  Lines        4743     4756      +13     
==========================================
+ Hits         3927     3940      +13     
  Misses        816      816              

Files	Coverage Δ
...penSpaceToolkit/Astrodynamics/Trajectory/State.cpp	100.00% <100.00%> (ø)
...trodynamics/Trajectory/State/CoordinatesBroker.cpp	95.38% <100.00%> (+0.94%)	⬆️

[vishwa2710]

Looks great!