Ability to Set Duty Time Sensor

**Describe the problem you have/What new integration you would like**

Add the ability to set the time for duty time. This would allow you to store the value in a global variable on an interval. The value could then be restored to the sensor value on startup. Currently, without being able to set the duty_time, the only way to restore the value is using `restore`. This method gives the warning that it could wear out the flash.

**Please describe your use case for this integration and alternatives you've tried:**

The use case it to try and preserve the flash.

**Additional context**

Example
```yaml
sensor:
- platform: duty_time
id: duty_time_daily
name: Daily Runtime
lambda: |-
return id(valve).state;
restore: False
update_interval: 60s

# Global variables store the duty times
# This is to preserve flash and not write every few seconds.
globals:
- id: global_duty_time_daily
type: int
restore_value: True

interval:
# Save to global
- interval: 5min # whatever interval
then:
- lambda: |-
id(global_duty_time_daily) = id(duty_time_daily).state;

esphome:
on_boot:
then:
- duty_time.set: # <- this would now be possible
id: duty_time_daily
value: !lambda 'return id(global_duty_time_daily);'
```

No files or tests are named. Start by locating the duty_time sensor implementation and its existing restore handling, then trace how sensor actions are declared and initialized at on_boot. Done means the YAML example can set the stored duty time without relying on frequent flash writes.

Written by the indexing model from the issue text.