fluent-plugin-prometheus : Provide way to remove metric samples that are not published anymore

[yeplaa]

Hi,
As mentioned on fluent/fluent-plugin-prometheus#20 issue, with the fluent-plugin-prometheus plugin, It seems currently exporter has no way to stop displaying metrics samples which are obsolete(never going to be updated).
On Kubernetes environment, it's problematic with many samples created (related to containers created).
The problematic is know, do you know if it's resolved or if a workaround is available?