service for fan_speed_next

[rossi75]

Is your feature request related to a problem? Please describe.

The "next mode"-service is still available for mop mode and mop intensity.

Describe the solution you'd like

Please add a service for the next fan_speed

Describe alternatives you've considered

Vacuum

Roborock S7 Pro Ultra

Additional context

attributes from [vacuum.roborock_s7_pro_ultra]: fan_speed_list: off, quiet, balanced, turbo, max, custom, max_plus mop_mode_list: standard, deep, custom, deep_plus mop_intensity_list: off, mild, moderate, intense, custom fan_speed: turbo

Mqtt request