feat: add SQLite3 config synchronous

[michalsn]

Description This PR adds support for the synchronous setting in SQLite3. It's not persistent across connections, which means it resets to the default (usually 2) with every new connection. We must set synchronous on each connection if we want it to differ from the default.

More info about this setting: https://www.sqlite.org/pragma.html#pragma_synchronous

Checklist:

• [x] Securely signed commits
• [x] Component(s) with PHPDoc blocks, only if necessary or adds value
• [ ] Unit testing, with >80% coverage
• [x] User guide updated
• [x] Conforms to style guide