Feature/seq editor cleanup

[cohansen]

Addresses all of the IN PROGRESS tasks in https://github.com/NASA-AMMOS/aerie-ui/issues/1291.

[AaronPlave]

Missing this item from the in progress list:

Empty state for third column in sequence editor

[cohansen]

Missing this item from the in progress list:

Empty state for third column in sequence editor

I added this empty state to the selected command editor, unless this isn't what you were referencing?

[AaronPlave]

Missing this item from the in progress list:

Empty state for third column in sequence editor

I added this empty state to the selected command editor, unless this isn't what you were referencing?

Ah I see, have to select a parcel first, thanks. Could you add st-typography-body?

[duranb]

I'm also getting a subscription error on /parcels/new

    "extensions": {
        "code": "validation-failed",
        "path": "$.selectionSet.parcel_to_parameter_dictionary.args.where.parcel_id._eq"
    },
    "message": "unexpected null value for type 'Int'"
}

[cohansen]

@AaronPlave and @duranb this is ready for a re-review.