The `AccountAliasAccessor` and the way it is used is incredibly convoluted. It is only used in the `AWSAccountAlias` class, which is also an overlapping name of a Django model. This `AWSAccountAlias` is only used in the `AccountLabel` class. This AccountLabel class is called during data ingestion here.

Perhaps there was an idea that future provider types besides AWS would need similar functionality, but that has not panned out (or we implemented it in a very different way). Either way, this labelling is performed in `prepare_monthly_report_sources`.

We should convert all of this into a simpler function call that is only run when we are processing an AWS provider type. The goal is to remove `AccountAliasAccessor`, `AWSAccountAlias`, and `AccountLabel`.