[Feature] Rename Dataset -> Collection

[jcace]

We're standardizing on the collection name throughout our stack, on the Edge-URID side, but also we need to make this change within DDM for consistency.

The collection name is more general than dataset and when new content is uploaded to an Edge node, it will be tagged with its collection, which will be managed in DDM when the dealmaking logic happens.

Changes to be made:

• Rename Dataset db struct to Collection
• Change reference columns (ex, DatasetID in WalletDatasets to CollectionID)
• Write DB migration in db/migrations.go for the table and column renames
• Rename api/datasets.go -> api/collections.go
• Update api/collections.go, renaming dataset to collection everywhere, changing routes so they are at /api/v1/collections instead of /api/v1/datasets
• Update all other API routes that refer to dataset, change to collection
• Rename /cmd/dataset.go, to /cmd/collection.go. Rename dataset to collection everywhere in the cmd cli commands
• Update documentation /docs/ , update API docs and CMD docs. Update readme.md and change all references of dataset to collection

https://filecoinproject.slack.com/archives/C058LSNP4KB/p1687917725397139?thread_ts=1687906985.717809&cid=C058LSNP4KB