Add DimmerRange for PWM lights (#8120)

[s-hadinger]

Description:

DimmerRange is now applied to PWM lights. This allows to set a minimum PMW value for non-zero levels. This is required for PMW_DIMMER and Mi Desk Lamp.

DimmerRange levels are 0..100 and gamma correction is applied if required.

To set the minimum value, set one channel to max value, ex: Color FF0000 then use Dimmer <x> to reduce brightness until the light turns off, and set DimmerRange to this value + 1. With LedTable 1, the minimum value is usually 35-40.

Related issue (if applicable): fixes #8120

Checklist:

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• Only relevant files were touched
• Only one feature/fix was added per PR.
• The code change is tested and works on core Tasmota_core_stage
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