Pass vec to range sync batch

[dapplion]

Issue Addressed

Non-urgent clean-up possible after

• https://github.com/sigp/lighthouse/pull/5583

This can wait for after v5.2.0

Currently we are:

• Fetching an entire Vec of blocks in the network context
• Constructing a stream with None terminator in sync manager
• Batch handles each block individually

Proposed Changes

Instead, we can just pass the vec from the network context to the batch

All logic in unchanged, most of the diff is a change in indentation