refactor: remove grid fields dependency from develop

[dmuldrew]

Purpose

This removes the recent grid field object dependencies from develop.

What is the code doing

From looking at git blame, the new changes I kept are grid equality, engine selection, removing the Seaborn dependency, and plotting color changes. It was pretty straightforward to search for grid[ to find the code using the dictionary access to grid.

Grid equality used the new objects pretty extensively so I refactored according to this current grid. I used the pandas provided assert_frame_equal test for dataframes.

Validation

All existing tests pass

Time to review

1 hour?

[dmuldrew]

I think I've migrated over the grid equality function now, though Daniel will know for sure.

[danielolsen]

We can't use all of the same tests as in #152, because the base grid no longer matches what's in scenario 419, but the most simple test fails:

>>> from powersimdata.input.grid import Grid
>>> grid1 = Grid(['Western'])
Reading bus.csv
Reading plant.csv
Reading gencost.csv
Reading branch.csv
Reading dcline.csv
Reading sub.csv
Reading bus2sub.csv
Reading zone.csv
>>> grid2 = Grid(['Western'])
Reading bus.csv
Reading plant.csv
Reading gencost.csv
Reading branch.csv
Reading dcline.csv
Reading sub.csv
Reading bus2sub.csv
Reading zone.csv
>>> grid1 == grid2
False

[danielolsen]

Tests were not added in #152, and that is my fault, but we want to be sure that this change does not break Grid equality. You can run simple tests that do not involve accessing scenarios on the server, and they should be able to show that two fresh copies of the grid evaluate equal, and that any modification to any of the dataframes causes two grids to evaluate as not equal.

[danielolsen]

You can also repeat all the checks that were done in #152 by manually copying the powersimdata/input/data/usa_tamu folder contents as they were at the time. Then a fresh Grid should evaluate as equal to the grid from the server.

[danielolsen]

I added a series of tests to the Grid equality check, see #183.

[dmuldrew]

All new grid equality tests pass now

[rouille]

All tests pass, including the most recent ones testing equality between two Grid objects. I believe all modules using the fields attribute have been refacored. Thank you very much. Also, do not forget to rebase before merging.