When time-only attributes are used with timezone-aware settings, they can
be incorrectly marked as changed due to date shifts during timezone
conversion. This happens because timezone conversions can change the
internal date component (e.g., from 2000-01-01 to 2000-01-02) even though
the time value remains the same.
This commit adds a new configuration option use_fixed_date_for_time_attributes
that, when enabled, ensures time-only attributes maintain a fixed date of
2000-01-01 during timezone conversions. This prevents false positive dirty
tracking while maintaining backward compatibility by defaulting to false.
Example usage:
  config.active_record.use_fixed_date_for_time_attributes = true
Fixes rails#55118
Co-Authored-By: Jean Boussier <jean.boussier@gmail.com>