fix: resolve UTF-8 encoding and complete postgres to gaussdb refactoring

UTF-8 Encoding Fixes:
- Fixed corrupted Japanese characters in test files: イロハニホヘトチリヌルヲ
- Resolved compilation errors caused by invalid character encoding in smol_str_01.rs
- Updated all test files to use proper UTF-8 encoding

Protocol Reference Updates:
- Updated all postgres_protocol imports to gaussdb_protocol in gaussdb-types
- Fixed remaining import inconsistencies across all packages
- Ensured all internal references use gaussdb naming convention

Documentation Updates:
- Updated gaussdb-protocol lib.rs: 'Low level GaussDB protocol APIs'
- Updated type definitions: 'GaussDB OID' and 'GaussDB Log Sequence Number'
- Updated backend message documentation: 'GaussDB backend messages'
- Improved crate descriptions for GaussDB focus

Code Quality Improvements:
- Fixed clippy warnings in authentication module (removed unnecessary borrowing)
- Applied cargo fmt for consistent code formatting across all packages
- Cleaned up unused imports and compiler warnings

Test Results:
- gaussdb: 18/22 tests passing (4 ignored - expected for missing DB connection)
- gaussdb-derive-test: 26/26 tests passing (100% success rate)
- gaussdb-protocol: 29/29 tests passing (100% success rate)
- tokio-gaussdb: 5/5 tests passing (100% success rate)

All packages now compile successfully with consistent naming and proper encoding.

Author: louloulin