Add PostgreSQL error condition names and comprehensive detail parsing

- Add comprehensive mapping of PostgreSQL error codes to condition names using StaticStringMap
- Add 'condition' field to PostgresError with human-readable condition names
- Add parsed detail fields for multiple PostgreSQL error types:
  * Unique violations: key, value
  * Foreign key violations: key, value, referenced_table
  * Not null violations: failing_column
- Support all standard PostgreSQL error codes from documentation (200+ codes)
- Use efficient StaticStringMap for O(1) error code lookups
- Replace magic numbers with named constants for better maintainability
- Remove unit tests that didn't test actual functionality (as requested by reviewers)
- Add comprehensive integration tests for multiple error types
- Extend parsing beyond just unique constraints to cover major error categories

This addresses the feedback that the implementation "feels incomplete currently" by:
1. Supporting multiple error types with structured detail parsing
2. Providing meaningful parsed fields for each error type
3. Adding real integration tests that verify actual functionality

Fixes #21698

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: Claude Bot