Rename status stores to trackers

[patchwork01]

Background

For checking the status of queries we use a store called the query tracker.

For checking the status of compaction and ingest jobs and tasks we use stores called the status stores.

We also have the state store, which sounds a lot like status store.

Description

We'd like to rename the compaction and ingest status stores to call them job trackers and task trackers instead, to distinguish them from the state store.

Analysis

We probably want to split this up to handle each status store separately. We'll need to make this change in the deployment of the underlying DynamoDB tables, in the actual implementation code, and in the reporting.

We'll also need to update the documentation everywhere the status stores are mentioned to call them job and task trackers instead.

We also need a bit more of the model of the trackers in the core module to include some of the data for a status update in a transaction. We could take this opportunity to rearrange the packages to put most of the status store core code into the core module in one place.