Expose mongodb_exporter version metric

[tumd]

Is your feature request related to a problem? Please describe. While debugging an issue with one of our mongodb clusters, it was very helpful to be able to establish mongodb version upgrade-path & dates, which is exported in the mongodb_version_info-metric. The same version information would be helpful related to mongodb_exporter itself.

Describe the solution you'd like Add a similar metric like mongodb_version_info but for mongodb_exporter itself. It should contain at least a label with the version, and preferably also include labels with commit and perhaps build_date.

Describe alternatives you've considered None.

Additional context Something like;

mongodb_exporter_version_info{version="0.36.0", commit="917800b", build_date="2023-01-03T11:57:03Z"} 1

[linrl3]

@BupycHuk @tumd Can I create a PR for this?