Consider always displaying the marker name in the marker chart

[julienw]

Coming from @nordzilla, it would be good to show the marker names in the marker chart, even when they're long. Erik would like to be able to resize the marker name column, but that's not super easy currently.

One idea is to have an hybrid method compared to what we have with the active tab view (see example: https://share.firefox.dev/42UA8v2).

Of course we'd still keep the column, but the marker name would "leak out", just the outside part would disappear on hover.

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