Improve existing upload metrics image experience

Note: This issue originated from discussions in this related issue.

Release Notes

Improve existing upload metrics image experience https://docs.gitlab.com/ee/operations/incident_management/incidents.html#metrics

Problems to be solved

1. It's not obvious that links added to charts are, in fact, links, because we're displaying the file name rather than a URL:

1. Links can only be added when the image is uploaded, not after the fact. So, if you don't immediately add a link, you have to delete the image and start over. Links that have been added also can't be edited.
2. It's not very easy to quickly add multiple images. Speed is important when it comes to uploading images. From Dave Smith:

Sometimes as an incident manager, I'm adding 2 or 3 screenshots while trying to pay attention to what we are doing in the incident room.

Proposal

1. Displaying the link and an external link icon when a URL has been added to an image:

2. Ease the process for uploading multiple images by closing the upload dialog as soon as the upload button is clicked, rather than waiting for the upload to complete. This may mean it will be difficult for us to determine which upload has failed, if there are multiple. But, we can modify the error message to indicate this as follows:

3. Introduce a link button on image uploads. This will allow us to edit already added links, as well as to introduce links on images that have already been uploaded. See designs below for additional details.

Designs

Adding a link to an already uploaded image

Hover tooltip	Add link modal

Editing an already added link

Hover tooltip	Edit link modal	Updated link, with replacement text

Figma file

Intended users

• Sidney (Systems Administrator)

Metrics

Increase adoption of alerts, in particular Monitor - AMAU - Alerts Active Users