Dev pwm refactor

[sjpark608]

Closes #315 PWM refactor

• init_pwm() method to instantiate and open a pwm device
• set_conifg() set pwm parameters
• enable() refactored to always enable the signal

[github-actions[bot]]

Package	Line Rate	Branch Rate	Health
adc	89%	85%	✔
calibration	86%	89%	✔
dac	100%	97%	✔
digital_input	100%	100%	✔
digital_output	98%	95%	✔
gpio	98%	94%	✔
led	0%	0%	❌
peripherals	92%	100%	✔
pwm	99%	96%	✔
reg_helper	97%	85%	✔
relay	100%	100%	✔
tc	98%	98%	✔
utilities	100%	100%	✔
Summary	93% (2669 / 2878)	92% (546 / 595)	✔