Improve regex filtering in surfacers

[robpickerill]

From: #583 / #583 (comment)

 I think we'll need to have something more generic, something like
map<string, string> allowed_metrics
map<string, string> ignore_metrics
where key is the label key, and value is a regex.

Moving this comment to an issue so that its not lost in the PR.

[manugarg]

Thanks for capturing it here, @robpickerill.

I'll soon submit a change for this.

[manugarg]

#597 should fix this.

[robpickerill]

Thanks Manu, I started on this PR to update the docs to help out: #598

[manugarg]

Closing this. Release will be tracked through the milestone v0.11.3.