Add alerts list widget to dashboard groups

[lambcode]

This update lets users manage the alerts list widget on metric dashbaords through terraform. An example dashboard looks like this. Note the difference in label (terraform) vs labels (public api). Also predicate and predicates. This was done to make the terraform look more ergonomic. LMK if you think this is too much overhead.

resource "lightstep_metric_dashboard" "test" {
	project_name          = "project"
	dashboard_name        = "Acceptance Test Dashboard (TestAccDashboardAlertsListPanel)"
	dashboard_description = "Dashboard to test the alerts list panel"

group {
	rank = 0
	visibility_type = "implicit"

	alerts_list_panel {
		name = "test_alerts_list_panel"

		x_pos = 0
		y_pos = 0
		width = 10
		height = 10 

            panel_options {
                sort_direction = "asc"
                sort_by = "status"
            }
            filter_by {
		predicate {
		    operator = "eq"
                     label {
                        key = "food"
                        value = "pizza"
                    }
                    label {
                        key = "food"
                        value = "burger"
                    }
                }
		predicate {
			   operator = "neq"
                            label {
                                key = "drink"
                                value = "coke"
                            }
                        }
                    }
	      }
	}
}

[gontzess]

LGTM! 🚀