add RavenDB integration

[TheGoldenPlatypus]

What does this PR do?

Adds a new integration for RavenDB using the OpenMetrics endpoint.
The integration collects server, cluster, database, index, and GC metrics from RavenDB and exposes them to Datadog. It also includes configurable filtering to control metric cardinality and a sample dashboard for visualization.

Motivation

RavenDB exposes Prometheus/OpenMetrics metrics, but there is currently no official Datadog integration.
This integration allows users to monitor RavenDB instances directly through Datadog without needing custom metric pipelines, while also providing controls to avoid high-cardinality metric ingestion.

Review checklist

• PR has a meaningful title or PR has the no-changelog label attached
• Feature or bugfix has tests
• Git history is clean
• If PR impacts documentation, docs team has been notified or an issue has been opened on the documentation repo
• If this PR includes a log pipeline, please add a description describing the remappers and processors.

Additional Notes

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[TheGoldenPlatypus]

the manifest validation is failing because source_type_id is required and must be unique
I don't have it, assumed the scaffolding should take care of assigning one.
Could you reviewers assign the correct source_type_id ?

{'assets': {'integration': {'source_type_id': ['Missing data for required field.']}}}

[github-actions]

This pull request has not been updated for more than 21 days. If there are no updates to this PR within 7 days, it will be closed. If you'd like to re-open this PR after it's been closed, you can start from the latest master branch or pull the latest changes into your branch and create a new pull request.

[TheGoldenPlatypus]

hey, following up on this PR as it's close to becoming stale. Any update or feedback from the team?