Phil/agent fixes

[psFried]

Description:

Rolls up a few different fixes for agent:

• Prevent null bytes from getting into live/built specs
• Handle errors in publications and controllers more gracefully
• Process controller jobs sooner

Individual commit messages have more details.

Notes for reviewers:

The default backoff for controller errors is pretty steep, and also uses a very large random jitter. This is to prevent thundering herd scenarios in case there's a widespread problem that causes a large proportion of controller jobs to fail.

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This change is 

[psFried]

Here's a scenario I've tested locally:

• Setup a webhook capture with schema inference, and a materialization to postgres
• Ingest a document with a \u0000 in one of the property names, and observe that the inferred schema is updated to reflect that
• The next controller run for the collection fails with an error about the null byte in the spec, and is set to retry
• Pull and edit the collection spec to no longer use the inferred schema
• After publishing the updated collection spec, the controller error clears