fluentd-elasticsearch: Support adding relabelings to ServiceMonitor

[robinkb]

Signed-off-by: Robin Ketelbuters robin.ketelbuters@gmail.be

What this PR does / why we need it:

This PR adds support for filling in the relabelings and metricRelabelings fields in the ServiceMonitor definition for fluentd-elasticsearch. For my specific use-case, I want to add labels to the fluentd_tail_file_position metric by extracting the information from the path label.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [x] Chart Version bumped (if the pr is an update to an existing chart)
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [fluentd-elasticsearch])

[robinkb]

Sorry, I was about to do so after opening the PR, but I got distracted. They've been added now.