Fix Alpine Linux disk usage metrics and keywords list as sample data

Changed

• Fix disk usage returning a Vec with no entries on Alpine Linux when the df --local command fails.

• Add support for lists in the sample data as root values on spans, as shown below. Previously we only supported lists as nested objects in maps.

  Elixir

  Appsignal.Span.set_sample_data(
    Appsignal.Tracer.root_span,
    "custom_data",
    [
      "value 1",
      "value 2"
    ]
  )

Removed

• Remove the appsignal_set_host_gauge and appsignal_set_process_gauge extension functions. These functions were already deprecated and did not report any metrics.

Fixed

• Fix missing error metrics for the error rate and error count graphs in some scenarios, like with Node.js Koa apps.

• Add support for keywords lists in sample data on spans. These would previously be shown an empty list.

  Elixir

  Appsignal.Span.set_sample_data(
    Appsignal.Tracer.root_span,
    "custom_data",
    %{"keyword_list": [foo: "some value", "bar": "other value"]}
  )

See the changelog for AppSignal for Elixir package 2.8.1 for more information.