Change PWM implementation to Arduino #7231

[s-hadinger]

Description:

Changed the implementation of PWM to one of the candidates from Arduino Core esp8266/Arduino#7231

This PR proved very stable at 80MHz and 160MHz, no visible flickering, phase alignment, reduced Interrupt pressure, and good behavior during the short interrupt storm during Wifi connection.

Also dropped support for Arduino Core 2.3.0, 2.4.1, 2.4.2.

Checklist:

• The pull request is done against the latest dev branch
• Only relevant files were touched
• Only one feature/fix was added per PR.
• The code change is tested and works on core Tasmota_core_stage
• The code change pass travis tests. Your PR cannot be merged unless tests pass
• I accept the CLA.

[s-hadinger]

Compilation broken, hold on.