Implement mass matrix in Barker's kernel

[AdrienCorenflos]

Barker's proposal should take in a mass matrix for pre-conditioning. The change should follow appendix G here https://arxiv.org/abs/1908.11812 and the interface of HMC

blackjax/blackjax/mcmc/hmc.py

Line 120 in 4a11236

inverse_mass_matrix: metrics.MetricTypes,

As a unit test, the implementer should check that barker for π(x) with mass matrix M has exactly the same outputs as the scaled version as per appendix G.