drivers: sensor: vl53l0x: add support to reprogram I2C address

The I2C address of the VL53L0X distance sensor can only be programmed
over the I2C bus. To do this:

1. The sensor is powered off or in standby mode
2. Power up the sensor, it boots with a default I2C address (0x29)
3. The I2C master sends a configuration command to set the new address
4. The sensor now communicates at the new address

In case there are more than one such sensor on the bus, they all have
the same address when starting up. We therefore need to first apply
step 1. on all of them. Then, sensor by sensor apply steps 2. to 4.

Because simple designs may not need to reprogram the address, we
introduce a new configuration option CONFIG_VL53L0X_RECONFIGURE_ADDRESS

If this setting is disabled, then the driver behaves as before.

If CONFIG_VL53L0X_RECONFIGURE_ADDRESS is enabled, then the driver does
the following:

- In vl53l0x_init(), apply step 1. This is done when the driver is
  brought up when starting the system
- in vl53l0x_start(), apply steps 2. to 4. This is done when fetching
  a sample, if the sensor has not been started yet.

Also, as cosmetic changes:
- add parenthesis around sub conditions in call to __ASSERT_NO_MSG
- gracefully handle unknown sensor channels in vl53l0x_channel_get

Signed-off-by: Titouan Christophe <moiandme@gmail.com>