[CHIA-1281] look-up generators in bulk (during reorg)

[arvidn]

Purpose:

Make potentially fewer DB queries for looking up generator references during reorgs (where they are looked up by block hash instead of height)

Current Behavior:

We look up generators one at a time.

New Behavior:

We look up all generators in one query.

[coveralls-official]

Pull Request Test Coverage Report for Build 14329159265

Details

• 39 of 39 (100.0%) changed or added relevant lines in 3 files are covered.
• 18 unchanged lines in 7 files lost coverage.
• Overall coverage increased (+0.02%) to 91.295%

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Files with Coverage Reduction	New Missed Lines	%
chia/full_node/full_node_api.py	1	85.07%
chia/_tests/core/full_node/stores/test_block_store.py	1	99.3%
chia/_tests/simulation/test_simulation.py	1	96.47%
chia/wallet/wallet_node.py	1	87.97%
chia/full_node/full_node.py	3	86.33%
chia/server/node_discovery.py	4	82.26%
chia/server/address_manager.py	7	91.38%

Totals
Change from base Build 14318635627:	0.02%
Covered Lines:	101413
Relevant Lines:	110941

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💛 - Coveralls