feat: Add modern extend for 'text' converter

[chdefrene]

• Add modern extend for 'text' converter
• Convert ELKO 4523430 to use 'text' modern extend

Related fix:

• Use correct value for 'regulator_mode' for ELKO 4523430 (noticed different readings on the thermostat display vs. Z2M)

[chdefrene]

I have not removed this toZigbee converter, since it is used for a device specific rule regarding max allowed characters.

https://github.com/Koenkk/zigbee-herdsman-converters/pull/7846/files#diff-51715221d06da600c3567799bdf03b1c7c25252c45217ff9af22702a4830dc32R43

[Koenkk]

@chdefrene in order to get rid of the toZigbee converter, we can add an extra argument to the text modernExtend: validate, which is a optional function to validate the input.

[chdefrene]

Sorry for the long wait, but I have applied the change now 🙂

[Koenkk]

Thanks!