api: /chain/blockToDate now fallbacks to fetching timestamp from indexer

[altergui]

hotfix cherrypicked from #1329

[altergui]

before: curl http://127.0.0.1:19090/v2/chain/blockToDate/2 {"date":"0001-01-01T00:00:00Z"}

after: curl http://127.0.0.1:19090/v2/chain/blockToDate/2 {"date":"2023-10-24T14:10:55.831423637Z"}

[coveralls]

Pull Request Test Coverage Report for Build 9545577240

Details

• 0 of 6 (0.0%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.02%) to 61.304%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
api/chain.go	0	6	0.0%
<!--	Total:	0	6	0.0%	-->

Files with Coverage Reduction	New Missed Lines	%
vochain/indexer/indexer.go	2	68.27%
vochain/state/account.go	2	67.08%
vochain/transaction/election_tx.go	2	61.54%
<!--	Total:	6		-->

Totals
Change from base Build 9545111263:	-0.02%
Covered Lines:	15909
Relevant Lines:	25951

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💛 - Coveralls