Berry provide lightweight options for tasmota.wifi/eth/memory/rtc

[s-hadinger]

Description:

Berry, this PR provides simplified alternative calls for tasmota.wifi(), tasmota.eth(), tasmota.rtc(), tasmota.memory(). These calls normally returns maps, which implies allocating a new map object on the heap. Now you can specify the name of the value you are interested in, and it returns only this value without allocating a new object.

tasmota.memory()
# {'heap_free': 136, 'program_free': 999, 'program': 1880, 'stack_low': 3.76562, 'iram_free': 33, 'frag': 21, 'flash': 4096, 'stack_size': 8, 'flash_real': 4096}

tasmota.memory('heap_free')
# 136

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.2.0.14
• I accept the CLA.

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