pre_validate_blocks_multiprocessing Warm up the cache once per batch

[arvidn]

Purpose:

This is a small improvement towards a more efficient long sync.

The section this patch moves makes sure the block record cache contains sufficient blocks going back from the current block.
Currently we do this inside the loop over the blocks in the batch, which is unnecessary. The batch is expected to be contiguous anyway, so warming up the cache once outside the loop is sufficient.

This offers a small speed-up and slight simplification to pre_validate_blocks_multiprocessing(). Although, this code should ideally be moved to where we start a long sync (or maybe even a deep reorg). The code was only added to address issues in deep reorgs, where the cache may be cold.

The sync rate goes from ~24 blocks/second to ~28 blocks/second. A speedup of ~ 1.16

This commit is probably best reviewed with whitespaces ignored, as it changes the indentation level for the code in question.

Current Behavior:

Warm up the cache for every block.

New Behavior:

Warm up the cache once, for the first block.

Testing Notes:

Sync test here.

[coveralls-official]

Pull Request Test Coverage Report for Build 10439213317

Details

• 13 of 13 (100.0%) changed or added relevant lines in 1 file are covered.
• 34 unchanged lines in 11 files lost coverage.
• Overall coverage increased (+0.01%) to 90.866%

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Files with Coverage Reduction	New Missed Lines	%
chia/daemon/keychain_proxy.py	1	73.03%
chia/rpc/rpc_server.py	1	88.82%
chia/farmer/farmer.py	1	73.79%
chia/_tests/core/full_node/test_transactions.py	1	99.14%
chia/wallet/util/wallet_sync_utils.py	1	86.54%
chia/server/node_discovery.py	1	79.43%
chia/full_node/full_node.py	2	85.85%
chia/daemon/client.py	2	73.33%
chia/full_node/full_node_api.py	5	82.49%
chia/wallet/wallet_node.py	7	88.51%

Totals
Change from base Build 10423078207:	0.01%
Covered Lines:	101335
Relevant Lines:	111501

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💛 - Coveralls

[wjblanke]

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