Feature: Add sub-check for Ingest Pipelines

[martialblog]

We can use the Node Stats API to check the ingest statistics for the node/pipelines.

There we can find: failed (integer) Total number of failed operations for the ingest node/pipeline.

I'd suggest a new sub-check for that

check_elasticsearch ingest
# Checks the Nodes Ingest Stats

check_elasticsearch ingest --pipeline example
# Checks the Ingest Stats for the pipeline "example"

Not sure yet if this needs a warning/critical threshold or is a boolean.