switch rust wrapper for sqlite in chia-tools

[arvidn]

rusqlite appears to be much more established and popular in the rust ecosystem. But more importantly, it has much more complete support for sqlite features, which are required for the event-log analysis tool I'm building.

While working in these files, I took the opportunity to transition test_block_generators.rs to use the (somewhat new) higher level abstraction to iterate over the transaction blocks in a blockchain database. This reduces a fair amount of duplicated code.

[coveralls-official]

Pull Request Test Coverage Report for Build 7098705134

• 0 of 14 (0.0%) changed or added relevant lines in 1 file are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 86.156%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
chia-tools/src/visit_spends.rs	0	14	0.0%

Files with Coverage Reduction	New Missed Lines	%
chia-tools/src/visit_spends.rs	1	0.0%

Totals
Change from base Build 7093492066:	-0.2%
Covered Lines:	10878
Relevant Lines:	12626

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💛 - Coveralls