feat: add postgres driver

[github-actions[bot]]

Bencher

Report	Fri, March 29, 2024 at 18:27:25 UTC
Project	theseus-rs/rsql
Branch	add-postgres-driver
Testbed	localhost

Benchmark	Latency	Latency Results nanoseconds (ns)
postgresql-embedded	➖ (view plot)	804530000.000
sqlite	➖ (view plot)	497120.000

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.60714% with 19 lines in your changes are missing coverage. Please review.

Project coverage is 95.98%. Comparing base (35f2a2e) to head (e55a846).

Files	Patch %	Lines
rsql_core/src/drivers/postgres.rs	96.21%	19 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #93 +/- ## ========================================== + Coverage 95.93% 95.98% +0.04% ========================================== Files 71 72 +1 Lines 7277 7837 +560 ========================================== + Hits 6981 7522 +541 - Misses 296 315 +19 ```

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