Turn ArangoStore into a crawlee storage provider

[eaton]

Does what it says on the tin. It's not ultra-high priority, but it would be an easy way to get around some of the Request vs UniqueUrl issues: both would be easily queryable.

This may also include revisiting how the DataSet and Fragment Entity types are handled; they may be better matches for Crawlee-style Datasets and KVS data; if they're stored in Arango anyways, using the different storage approach wouldn't prevent us from doing complex queries with DS/KVS data.

[eaton]

This can be broken into a couple of steps:

• Custom request queue provider
• Custom Dataset provider
• Custom KVS provider
• Potentially use TypeFS for another KVS provider?