feat: Add PostgreSQL storage implementation for Torii

[cmackenzie1]

This commit introduces a PostgreSQL storage implementation for Torii. Adding this implementation highlighted an issue around nulls that wasn't caught by the sqlite implementation since it is flexible with types.

This crate requires docker compose up -d to be run (or a postgres instance to be available) for the tests to run.

Closes #3

[codecov]

Codecov Report

Attention: Patch coverage is 55.84192% with 257 lines in your changes missing coverage. Please review.

Project coverage is 65.57%. Comparing base (b40e8d2) to head (eefaf93).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
torii-storage-postgres/src/lib.rs	55.93%	256 Missing ⚠️
torii-core/src/plugin.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
- Coverage   68.78%   65.57%   -3.21%     
==========================================
  Files          11       12       +1     
  Lines        1746     2327     +581     
==========================================
+ Hits         1201     1526     +325     
- Misses        545      801     +256     

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