Support direct output to Time-Series databases

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

ESPHome is super handy for the framework it provides. However, the only way to get output at the moment, as far as I can determine is either:

- Write a custom MQTT forwarding agent
- Add-Ons to Hass.io

I have an existing time-series database (I actually have both graphite and am experimenting with an influxdb server, both of which have a fair bit of data in them already).

The hass.io extension for influxdb appears to be hard-coded to run it's own internal influxdb instance in docker, and (based on cursory reading) doesn't support using existing instances.
Additionally, I'd really prefer not **needing** the hass.io server in the first place.

Basically, it'd be nice if there was a way to have ESPHome ship sensor metrics directly to the time-series database. Shipping metrics to graphite is *super* lightweight (just squirt a UDP packet). InfluxDB is still straightforard, though a bit more stateful (it's a HTTP POST).

By doing this, the logging system is dramatically simplified.

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

The current options are:

- ESPHome Sensor -> MQTT Broker -> custom forwarding agent -> TS Database
- ESPHome Sensor -> Hass.io server -> extension -> Containerized (separate) TS Database

By having the sensor ship directly to the server, you get:

- ESPHome Sensor -> TS Database

So there's *much* less complexity, and points of failure.

**Additional context**

I'm already running my hass.io instance in a LXC container, so I can't use docker. The hard dependency (?) on docker is super annoying.

I *also* have a existing grafana instance. The insistence of the plugins to shove what are basically completely independent services into the hass interface is annoying when you're trying to use esphome as a component of an existing system, and you'd like to avoid having 2 instances of everything.