Refactor embed.vue charts(): from "Add empty region when group metrics are missing"

Background

Our value for metricsWithData changed from a statefully maintained variable to a getter in !20900 (merged).

This can allow the embed component to calculate charts() and move them the logic to a getter.

Proposal

Refactor this computed prop, which calculates which charts to display in a very round about way:

    charts() {
      if (!this.dashboard || !this.dashboard.panel_groups) {
        return [];
      }
      const groupWithMetrics = this.dashboard.panel_groups.find(group =>
        group.panels.find(chart => this.chartHasData(chart)),
      ) || { panels: [] };

      return groupWithMetrics.panels.filter(chart => this.chartHasData(chart));
    },

Original Discussion

The following discussion from !20900 (merged) should be addressed:

• @dbodicherla started a discussion: (+1 comment)

  question: I wonder if we should get call to metricsWithData() out of a loop.