Addition of Xray metrics

[Thravict]

Feature Description

Including Xray metrics like indexed repositories, database synchronization (success, last sync), etc.

Use Case(s)

Especially for alerting I see a need for things like the database synchronization as CVE's should be up to date.

PS:
I would really like to include this feature by myself in a pull request. But first I wanted to ask if Xray would be desired here at all or if it would be better to outsource it to a separate exporter.

[peimanja]

Thanks for the suggestion and volunteering to submit the PR to implement new metrics.
Xray metrics can be added in this exporter as long as:

• They are optional
• Same artifactory.url can be used
• Queries does not impact performance of Artifactory/XRay