Keep `BLOCKS_METADATA_BUFFER_SIZE` the same as current `SYNC_BATCH_SIZE`

[HonzaR]

Is your feature request related to a problem? Please describe.

We'd like to follow up on this issue, where we defined the ideal situation - using BLOCKS_METADATA_BUFFER_SIZE the same size as the sync batch. We use SYNC_BATCH_SIZE and then SYNC_BATCH_SMALL_SIZE for the sandblasting period, so the BLOCKS_METADATA_BUFFER_SIZE should reflect this.

Currently, we only raised the BLOCKS_METADATA_BUFFER_SIZE to 1000, which brings great sync machine speed up (about 50%) and still works well for the sandblasting period.

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