Fix sqlite busy errors

[jlewi]

Fix sqlite busy errors with session based learning

There were a couple different errors

• We were still enqueing block ids and not sessions in some places
• When we call Enqueue we should filter out sessions that aren't suitable for learning; this should minimize DB contention
• Improve logging

By default sqlite doesn't have any retries for SQLITE_BUSY errors. We could configure a timeout for retries using a PRAGMA; we should probably do that but I want to hold off to see if this PR fixes the contention.

• Filed #348 to follow up on this

Use ko to create docker images as part of the development process

• This is convenient when we want to build a docker image from our latest changes without doing a relase.
• Change the Dockerfile to not include any arguments so that it is compatible with the image ko builds

[netlify[bot]]

✅ Deploy Preview for foyle canceled.

Name	Link
🔨 Latest commit	fa84ee6550a15b023e8ee67888de45523871a3eb
🔍 Latest deploy log	https://app.netlify.com/sites/foyle/deploys/674402b8f7f4350009456316