--start-offset as non-negative float (relax equality to allow 0 as input)

[23pointsNorth]

Description

Currently, based on #931, the input cli param --start-offset has a default value of 0.0, yet is of type check_positive_float .

This creates the issue, that by default, the value is 0, yet one cannot set the value to 0 by not using hte default field. i.e.

ros2 bag run {bag_name} --start-offset 0 # this fails

ros2 bag run {bag_name}  # this works as expected, yet starts from 0

Completion Criteria

It would be great to relax the equality, as it would allow using the start-offset param as part of matrix scans in CI jobs and other places where a list of offsets may be chosen.

P.S. check_positive_float and positive_float have been used mixed within the argparse.