[mcap export]Agent information isn't being exported for the first step (step zero)

[francocipollone]

Summary

maliput_sim/maliput_sim/export/mcap.py

Line 149 in 1be6105

for sim_state in sim_states[1:]:

Due to that the states are being iterated as of the second sample the agent information (in scene update, and the pose and behavior infromation) is not being exported in the iteration zero.