Enable external Delta tables in Seafowl

[gruuya]

Utilize the Delta table factory for DataFusion, and the new options mechanism for creating external Delta tables in Seafowl.

Example definition for AWS S3-backed delta table:

CREATE EXTERNAL TABLE my_delta
STORED AS DELTATABLE
OPTIONS ('AWS_ACCESS_KEY_ID' 'secret', 'AWS_SECRET_ACCESS_KEY' 'also_secret', 'AWS_REGION' 'eu-west-3') 
LOCATION 's3://my-bucket/my-delta-table/'

[mildbyte]

Looks great! Do you know if the new deps make the final binary size much larger? Might be worth putting the support behind the Cargo features mechanism so that people can turn it off if necessary.

[mildbyte]

(tagging #175 since this partially solves it)

[gruuya]

Good point, thanks!

I've featurized remote/delta table querying mechanisms now (both are default), and measured the binary sizes in a couple of scenarios:

1. all features—65MB
2. all features except delta tables—58MB
3. all features except delta and remote tables—55MB

So delta tables contribute about 10% to the new binary size, with remote tables being much more lightweight.