Add sunrise, sunshine, sunset, and daylight tests

[wapcaplet]

Summary

SUMMARY: Infrastructure "Add tests for sun-related functions"

Purpose of change

To test functions in calendar.cpp related to the sun, in preparation for refactoring several of them, as a roundabout way of homing in on functionality related to the light levels of cloudy moonlit skies.

Peripherally related to #38697

Describe the solution

Adds test cases to tests/sun_test.cpp and refactors some related functions in src/calendar.cpp.

• New function added: is_day
• Functions renamed: is_sunrise_now to is_dawn, is_sunset_now to is_dusk
• Calendar functions tested: sunrise, sunset, is_night, is_dawn, is_dusk, is_day, sunlight, current_daylight_level, to_string, to_string_time_of_day

General sun-related behavior:

• First day of spring and autum mark the equinoxes
• First day of summer and winter mark the solstices
• Dawn starts at sunrise and lasts 1 hour (twilight duration)
• Dusk starts at sunset and lasts 1 hour
• Sunlight
  • Increases at dawn
  • Maximum during the day
  • Decreases at dusk
  • Only moonlight at night
• Sunrise and sunset
  • 7am - 5pm on winter solstice
  • 6am - 7pm on spring/autumn equinoxes
  • 5am - 9pm on summer solstice
• Max sunlight is
  • 75% on winter solstice
  • 100% on spring/autumn equinoxes
  • 125% on summer solstice

Describe alternatives you've considered

Darkness

Testing

tests/cata_test [sun]

Additional context

Pretty happy with the current state of this one.

[ifreund]

Thanks!