[Databases] Fix query behavior + general cleanup

[drkameleon]

Description

Right now, our database module suffers from various issues:

• execManySqliteDb has no ROLLBACK on failure
• we match select to figure out whether a query will return rows or not - this is totally fragile
• query pushes nothing on non-SELECT queries
• .id and the result itself can both be push to the stack ⚠️
• execManySqliteDb always returns EmptyQueryResult
• .mysql is obsolete/unused
• all values returned as strings - integers, floats, and NULLs are all stringified no matter what
• open doesn't handle errors properly
• also, the name is extremely common and could - perhaps be re-assigned to sth more suitable (e.g. file/stream access?)
• close doesn't catch errors properly either

Type of change

• Code cleanup
• Unit tests (added or updated unit-tests)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (implementation update, or general performance enhancements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (documentation-related additions)