Verify that `impute_region_ids=False` functions when ingesting NASC files

[brandynlucca]

Currently, NASC from the Echoview exports are integrated for the entire water column. When impute_region_ids=True in the consolidate_echoview_nasc function (and the default behavior of EchoPro), the first indexed region name is assigned to all of the NASC values in the water column, thus homogenizing them. When impute_region_ids=False, this is not the case; however, it is unclear whether multiple regions per interval would function as expected with downstream functions. So the downstream code needs to be validated to test this.

[brandynlucca]

Current status
Currently, Echopop mirrors the behavior of EchoPro when assigning region ID's (and therefore region class and haul number) to a given transect interval. When there is more than 1 region in a given interval that do not share the same region ID and region class, the interval is assigned these labels using only the top-most layer. Take for instance:

Interval 1
              [Region name | Region class| NASC]
Depth layer 1 [ Region1    | Hake        | 1000]
Depth layer 2 [ Region2    | Age-1 hake  | 500 ]
Depth layer 3 [ Region3    | Hake mix    | 500 ]

When integrating the NASC for this interval, the output is a single estimate of NASC (2000 m^2 nmi^-2) that would be labeled as Region 1 and Hake despite 50% of the NASC being attributed to Region2 and Region3.