feat: convert postgresclient module to independent sal-postgresclient package

- Move src/postgresclient/ to postgresclient/ package structure
- Add comprehensive test suite (28 tests) with real PostgreSQL operations
- Maintain Rhai integration with all 10 wrapper functions
- Update workspace configuration and dependencies
- Add complete documentation with usage examples
- Remove old module and update all references
- Ensure zero regressions in existing functionality

Closes: postgresclient monorepo conversion

postgresclient/tests/rhai/test_print.rhai

@@ -0,0 +1,24 @@
+// Simple test script to verify that the Rhai engine is working
+
+print("Hello, world!");
+
+// Try to access the PostgreSQL installer functions
+print("\nTrying to access PostgreSQL installer functions...");
+
+// Check if the pg_install function is defined
+print("pg_install function is defined: " + is_def_fn("pg_install"));
+
+// Print the available functions
+print("\nAvailable functions:");
+print("pg_connect: " + is_def_fn("pg_connect"));
+print("pg_ping: " + is_def_fn("pg_ping"));
+print("pg_reset: " + is_def_fn("pg_reset"));
+print("pg_execute: " + is_def_fn("pg_execute"));
+print("pg_query: " + is_def_fn("pg_query"));
+print("pg_query_one: " + is_def_fn("pg_query_one"));
+print("pg_install: " + is_def_fn("pg_install"));
+print("pg_create_database: " + is_def_fn("pg_create_database"));
+print("pg_execute_sql: " + is_def_fn("pg_execute_sql"));
+print("pg_is_running: " + is_def_fn("pg_is_running"));
+
+print("\nTest completed successfully!");