test: use precompiled statements in examples

[ligurio]

Prepared statements improve performance by caching the execution plan for a query after the query optimizer has found the best plan.

If the query doesn't have a complicated plan (such as simple selects/inserts with no joins), then prepared statements won't give you a big improvement since the optimizer will quickly find the best plan.

SQLite helpers has been renamed in test examples.

[coveralls]

Pull Request Test Coverage Report for Build 9254214822

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.6%) to 93.419%

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Files with Coverage Reduction	New Missed Lines	%
molly/tests.lua	4	87.93%
<!--	Total:	4		-->

Totals
Change from base Build 9254137959:	-0.6%
Covered Lines:	653
Relevant Lines:	699

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💛 - Coveralls