Get information about installed add-ons from the profiled Firefox instance

[firefox-devtools]

Get information about installed add-ons from the profiled Firefox instance

[past]

This seems to be fixed, I see this in the profile metadata:

    "extensions": {
      "length": 3,
      "id": [
        "[email protected]",
        "[email protected]",
        "[email protected]"
      ],
      "name": [
        "Web Compat",
        "Gecko Profiler",
        "Firefox Screenshots"
      ],
      "baseURL": [
        "moz-extension://f4bed81a-9270-9a42-bdba-4bbdb207d8c2/",
        "moz-extension://03cd68a9-c8a1-f24d-9bd0-4a55d791be33/",
        "moz-extension://0e5fa9e9-f09e-ab43-b5c1-df7799966ac1/"
      ]
    },

[julienw]

We still miss the icon but this is a good start !
We also need to surface it.

[fqueze]

The metadata panel implemented in #929 shows the list of add-ons.