Berry f-strings now support ':' in expression

[s-hadinger]

Description:

Berry, now f-strings supports ':' in expression, if double as '::'.

Example:

var is_on = true
var s = f"status = {is_on ? 'on' :: 'off'}"
# s is 'status = on'

f"status = {is_on ? 'on' :: 'off'}" is equivalent to format("status = %s", is_on ? 'on' : 'off')

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.3.1.3.250504
• I accept the CLA.

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