Rename experiment vue component

What does this MR do?

This is fixing a follow-up issue: #326334 (closed)

Vue recommends to have multi-worded components to not conflict them with HTML elements or web components. I am changing the experiment component from <experiment> to <gitlab-experiment> to have a multi-worded component and align with our other internal components that we have in pajamas.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

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