Clustering for pose estimation

[hidmic]

Feature description

Connected to https://github.com/Ekumen-OS/beluga/discussions/172. Good ol' AMCL computes sampled mean and covariance from particle clusters, whereas Beluga AMCL computes sampled mean and covariance for the entire posterior particle cloud. Regardless of any arguments in favor or against either approach, Beluga AMCL should offer the choice. We need another estimation mixin.