Time in lane issue tracking (for board)
### Description
When running down our board, we like to see how long a task has been in a lane (has a label) quickly so it is easy to tell which tickets are becoming stagnant. This information seems to already be tracked as it is possible to see when a label was added to a ticket in the ticket description.
### Proposal
Add a "time in lane" or "time with label" to the board view.
### Links / references
### Documentation blurb
#### Overview
* What is it?
A quick way to see if tickets are becoming stagnant.
* Why should someone use this feature?
Makes it easy for a leader to tell if something needs to be followed up on, or external resources nudged.
* What is the underlying (business) problem?
Tickets being made/tracked != tickets being finished if they aren't followed up on
* How do you use this feature?
We use it to make sure dependencies are being resolved and people are getting the resources required to finish the job.
#### Use cases
* Who is this for? Provide one or more use cases.
Anybody using the "board" view of issue tracking
### Feature checklist
Make sure these are completed before closing the issue,
with a link to the relevant commit.
- [ ] [Feature assurance](https://about.gitlab.com/handbook/product/#feature-assurance)
- [ ] Documentation
- [ ] Added to [features.yml](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/data/features.yml)
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