[grafana-agent] add Grafana Agent

[sbaerlocher]

Description

Addition of the Grafana Agent: https://grafana.com/docs/agent/latest/

Motivation and Context

Since the Grafana packages are already maintained by you, I thought that your repository for the agent is the right place.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Migrated package (a package has been migrated from another repository)

Checklist:

• My code follows the code style of this repository.
• My change requires a change to documentation (this usually means the notes in the description of a package).
• I have updated the documentation accordingly (this usually means the notes in the description of a package).
• All files are up to date with the latest Contributing Guidelines
• The added/modified package passed install/uninstall in the chocolatey test environment.
• The changes only affect a single package (not including meta package).

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[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[mkevenaar]

Hi @sbaerlocher,

Thank you for submitting this package, I have some small requests that needs to be changed. Could you update these please?

Thanks

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[mkevenaar]

LGTM!

[AppVeyorBot]

✅ Package verification completed without issues. PR is now pending human review

[mkevenaar]

@sbaerlocher your changes have been merged, thank you for your contribution!