libretiny: replace ledc with libretiny_pwm #31

Job	Run time
Create common environment	41s
yamllint	15s
Check black	14s
Check pyupgrade	17s
Run script/ci-custom	12s
Check clang-format	27s
Check flake8	13s
Run pytest	19s
Check pylint	1m 30s
Run YAML test 1	7m 15s
Run YAML test 2	2m 44s
Run YAML test 3	3m 25s
Run YAML test 3.1	2m 10s
Run YAML test 4	2m 50s
Run YAML test 5	4m 49s
Run YAML test 6	1m 21s
Run YAML test 7	1m 47s
Run YAML test 8	2m 7s
Run script/clang-tidy for ESP8266	5m 32s
Run script/clang-tidy for ESP32 Arduino 1/4	12m 59s
Run script/clang-tidy for ESP32 Arduino 2/4	10m 42s
Run script/clang-tidy for ESP32 Arduino 3/4	8m 52s
Run script/clang-tidy for ESP32 Arduino 4/4	9m 33s
Run script/clang-tidy for ESP32 IDF	3m 51s
CI Status	1s
	1h 24m 6s

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