Added Berry bytes().reverse() method

[s-hadinger]

Description:

Report from berry-lang/berry#308

Add bytes().reverse([idx:int, len:int, grouplen:int]) -> bytes() to reverse bytes or group of bytes in-place without allocating a new object.

By default all bytes are reversed, but you can reverse only a portion from idx of length len. You can also reverse group of bytes with grouplen, this is useful for WS2812 leds to reverse the order of leds in a matrix.

Fixed some compilation warnings.

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.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.5
• I accept the CLA.

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