Support sleep mode for Grow Fingerprint sensor

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

I want to be able to disable the Grow Fingerprint reader R502 when the ESP32 is put to sleep. This can be easily accomplished by always powering pin 6 (power for the fingerprint detector) and GND, and toggling ping 1 (VCC) with a transistor. This way, you can listen for finger detection and turn on pin 1 to communicate with the module, and turning it off after a timeout, or just before going to sleep.

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

The use case is for a battery-powered ESP32 fingerprint reader. This reader consumes 2uA of power with only the finger detection circuit enabled, but 30mA if the entire module is powered up.
As a workaround, I've tried to configure an [output](https://esphome.io/components/output/gpio.html) on a pin connected to an NPN transistor, and turn it on as early as possible using `on_boot` with priority 700, and off just before going to sleep. However, this setup does not work because there are only ~10ms between the transistor powered up and the first communication over UART that the sensor integration does. According to [the datasheet](https://cdn-shop.adafruit.com/product-files/4651/4651_R503+fingerprint+module+user+manual.pdf), it takes "<30 ms" to power up, but since the first call fails it cannot set up the component.
I have also tried using an automation delay after turning on the output in `on_boot`, but they work asynchronously and don't delay the components boot.

**Additional context**

I believe this should be integrated as part of the fingerprint module, with an extra `wakeup_pin` option to drive a transistor, and a `startup_delay` with a default value of 50ms or so to control how long to wait for the fingerprint to initialize.