Berry leds improve reuse of buffer

[s-hadinger]

Description:

Berry improve reuse of bytes() buffer in leds.pixels_buffer(old_buf) and create a new buffer in case the number of pixels changed on the fly.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.8
• The code change is tested and works with Tasmota core ESP32 V.3.1.0.241206
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass