Support InfluxDB line protocol in scrapers

I like InfluxDB line protocol very much for its simplicity and consistency. So, I usually push data from my services to InfluxDB in this protocol.
Recently, I wanted to switch to the pull-scheme and surprisingly found out that [Influx own scrapers](https://docs.influxdata.com/influxdb/v2/write-data/no-code/scrape-data/) do not support Influx’s own protocol :-(

I can write my own scraper, of course, but it would sound logical if InfluxDB supported its own protocol in its scraper.

__Proposal:__
Let scrapers support not only Prometheus protocol, but InfluxDB line protocol as well.

__Current behaviour:__
Currently the line protocol isn’t supported.

No repository files or tests are named. Start by reviewing the linked scraper documentation and locating the existing scraper protocol handling; done means scrapers accept and correctly process InfluxDB line protocol alongside the currently supported Prometheus protocol.

Written by the indexing model from the issue text.