Add postgres adapter

[aguspdana]

[!IMPORTANT] Add PostgreSQL adapter with client support, configuration, schema, data, and tests, including PostgreSQL-specific query handling and limitations.

• PostgreSQL Adapter:
  • Add PostgreSQL client support in src/index.ts and queryMachine.ts.
  • Implement PostgreSQL-specific query building and execution in pg/build.ts, pg/machine.ts, and pg/run.ts.
• Configuration:
  • Add PostgreSQL configuration in tests/adapters/postgresDB/mocks/config.ts.
  • Update init.ts to include PostgreSQL test configuration.
• Schema and Data:
  • Create PostgreSQL schema in schema.sql and data in data.sql.
• Testing:
  • Add postgres.sh for setting up PostgreSQL test environment.
  • Modify query.ts to include PostgreSQL-specific test cases and handle unsupported features.
  • Update package.json to include PostgreSQL dependencies and test scripts.
• Miscellaneous:
  • Update schema.ts to include PostgreSQL-specific configurations for roles and fields.

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