add diagnostics related to trips without trip weights and expanded sample sizes

[iantaylor-NOAA]

Is your feature request related to a problem? Please describe.
PacFIN data for Lingcod include lots of trips without trip weight, which end up with expansion factor of 1, whereas many trips have a reasonably large expansion, creating a bimodal distribution of expanded sample sizes and spikes in the resulting length compositions. An example of the resulting distribution is posted to pfmc-assessments/lingcod#69.

Describe the solution you'd like
A standard output table of the number of trips by gear/year that have missing trip weight would provide useful information.
@chantelwetzel-noaa also demonstrated that plotting the distribution of Final_Sample_Size by fleet/year is a useful way to see what's going on.

Describe alternatives you've considered
One-off scripts for any given species.

Additional context
Nothing now. Could be added later.