Batch more database operations to improve the performance

[MOZGIII]

Goes in after #513

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This PR extends the work done in the couple previous PRs to get the performance of the execution to production levels. As of this PR, the benches demonstrate respectable 114% workflows processing rate versus the old DAG-based approach.

	drain (25k)	throughput	vs DAG
Pre-batching	~26.8s	~935/s	0.36x (2.8x slower)
Legacy DAG	~9.7s	~2,586/s	1.0x
Batchers / median	~10.1s	~2,475/s	~0.96x
Batchers / best runs	~8.5s	~2,940/s	~1.14x

[github-actions]

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_{Compared to main branch}