[request]: Add additional labels on scraper level

[mpostument]

Use case. Why is this important?

Hello, i have multiple cloudwatch exporters running in the same eks cluster. But they are scraping metrics from different AWS account. And i don't have ability to identify from which AWS account i am using. Would be nice to have ability to define set of additional labels which is added to every metric available in cloudwatch scraper

Metric relabel on prometheus is not an option, because i am using auto discovery and not static scraping job

How do you think the new configuration should look like?

Example:

extraLabels:
  account_name: AWSAccount1
  env: Prod