13.2.0: SQLite forward compatibility

• Implemented forward compatibility for SQLite error handling, see
  https://wiki.php.net/rfc/sqlite3_exceptions and #52
  (@thekid)
• Fixed empty string handling in TDS protocol for PHP 8.1+, see
  https://wiki.php.net/rfc/deprecate_null_to_scalar_internal_arg
  (@thekid)
• Fixed missing declaration for MySqlxProtocol::$fieldparser, see
  https://wiki.php.net/rfc/deprecate_dynamic_properties
  (@thekid)
• Fixed handling of MySQL error code 1927 ("Connection was killed")
  (@thekid)
• Overhauled test suite:
  . Migrated tests to new testing library, see xp-framework/rfc#344
  . Split unit and integration tests
  . Added PHP 8.3 and PHP 8.4 to the test matrix
  . Fixed integration tests to no longer reuse connections
  (@thekid)