allow define wifi credentials in pio

[Jason2866]

Description:

to make a standard build with own credentials possible without using user_config_override.h just by define them in Platformio. FR #21632

Checklist:

• [x] The pull request is done against the latest development branch
• [x] Only relevant files were touched
• [x] Only one feature/fix was added per PR and the code change compiles without warnings
• [x] The code change is tested and works with Tasmota core ESP8266 V.2.7.6
• [x] The code change is tested and works with Tasmota core ESP32 V.3.0.1
• [x] I accept the CLA.

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

[plu]

Thank you!