Signed-off-by: Paschalis Tsiliaspaschalis.tsilias@grafana.com

What this PR does / why we need it:
As stated in the linked Issue, there's currently no easy way toexclude files from a Promtail config, except for overly restrictive and/or complex glob patterns.

This addition may be helpful in a number of scenarios, from avoiding usage spikes in Grafana cloud, to having separate pipeline_stages for specific file formats, or filtering directories which Promtail couldn't tail due to permissions.

Since the upstream bmatcuk/doublestar package doesn't support negation patterns, this is another way of achieving the same result.

Which issue(s) this PR fixes:
Fixes#5744

Special notes for your reviewer:
From my local tests, this seems to work as intended both in scrape_config and file_sd_config blocks; let me know if I've missed anything ^^

Checklist

• Documentation added
• Tests updated
• Add an entry in theCHANGELOG.md about the changes.