test(storage): add postgres without prepared statements integration tests

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 64.68%. Comparing base (dd6a0a0) to head (e560735). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3455 +/- ## ========================================== - Coverage 64.69% 64.68% -0.01% ========================================== Files 174 174 Lines 13918 13920 +2 ========================================== Hits 9004 9004 - Misses 4225 4227 +2 Partials 689 689 ``` | [Flag](https://app.codecov.io/gh/flipt-io/flipt/pull/3455/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flipt-io) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/flipt-io/flipt/pull/3455/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flipt-io) | `64.68% <ø> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flipt-io#carryforward-flags-in-the-pull-request-comment) to find out more.

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