[Exploratory View] When loading one type of metric for a data type, all other metrics in other series also show as loading

[lucasfcosta]

Kibana version: 7.16 (SHA c5228354e5fdaf66f8466693f23f3d46d5632b88)

Elasticsearch version: 7.16

Server OS version: MacOS Big Sur 11.6

Browser version: Google Chrome Version 95.0.4638.69 (Official Build) (x86_64)

Browser OS version: MacOS Big Sur 11.6

Original install method (e.g. download page, yum, from source, etc.): I'm running Kibana from source, and connecting it to a 7.16-snapshot container from docker.elastic.co.

Describe the bug: When you fetch metrics for one data type, all the previous series' data type metrics also show as loading, even if they use a different data type.

Steps to reproduce:

1. Access the Exploratory View (Observability > Uptime > Analyze Data)
2. To make this behaviour easier to see, turn on network throttling (Slow 3G). You should be able to see this behaviour without the throttling, but the throttling helps to illustrate the problem.
3. Add a new series whose data-type is different from the pre-populated series' data type (RUM, for example)
4. See that the previous series' row also shows it's loading.
5. To see this again, add yet another series with a different data-type, like Mobile experience, for example. You'll see all previous series also display a loading state.

Expected behavior: Only the relevant series should display a loading state.

Screenshots (if relevant):

Errors in browser console (if relevant): None.

Provide logs and/or server output (if relevant): None.

Any additional context: I've found this while testing #115740.

Also, further refinement of the labels I added would be much appreciated. Thanks!

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)