[Vega] Add ability to open links in Vega in new window

[andrimal]

Summary

Fix #70745

Enables the option to open the clickable mark links of a Vega Visualization in a new tab.

To achieve this functionality:

• use the usermeta.embedOptions.loader property in the vega chart spec to pass the "target": "_blank" configuration:

"usermeta": {
    "embedOptions": {
      "loader": {"target": "_blank"}
    }
  }

Link opens in a new tab:

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Unit or functional tests were updated or added to match the most common scenarios
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

[dej611]

Vega spec to test:

{
  $schema: https://vega.github.io/schema/vega-lite/v5.json
  data: {
    url: {
      %context%: true
      %timefield%: @timestamp
      index: kibana_sample_data_logs
      body: {
        aggs: {
          countries: {
            terms: {
              field: geo.dest
              size: 25
            }
            aggs: {
              hours: {
                histogram: {
                  field: hour_of_day
                  interval: 1
                }
                aggs: {
                  unique: {
                    cardinality: {
                      field: clientip
                    }
                  }
                }
              }
            }
          }
        }
        size: 0
      }
    }
    format: {property: "aggregations.countries.buckets"}
  }
  
  transform: [
    {
      flatten: ["hours.buckets"],
      as: ["buckets"]
    },
    {
      filter: "datum.buckets.unique.value > 0"
    },
    {
    "calculate": "'https://www.iso.org/obp/ui/#iso:code:3166:' + datum.key", "as": "url"
    }
  ]

  mark: {
    type: rect
    tooltip: {
      expr: "{\"Unique Visitors\": datum.buckets.unique.value,\"geo.src\": datum.key,\"Hour\": datum.buckets.key}"
    }
    href: {
      expr: datum.url
    }
  }


  encoding: {
    x: {
      field: buckets.key
      type: nominal
      scale: {
        domain: {
          expr: "sequence(0, 24)"
        }
      }
      axis: {
        title: false
        labelAngle: 0
      }
    }
    y: {
      field: key
      type: nominal
      sort: {
        field: -buckets.unique.value
      }
      axis: {title: false}
    }
    color: {
      field: buckets.unique.value
      type: quantitative
      axis: {title: false}
      scale: {
        scheme: blues
      }
    }
  }
  "usermeta": {
    "embedOptions": {
      "loader": {"target": "_blank"}
    }
  }
}

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[andrimal]

/ci

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: d6f4f78

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
visTypeVega	2.0MB	2.0MB	+190.0B

History

• 💔 Build #292535 failed d31c594
• 💚 Build #290795 succeeded d172c6e
• 💛 Build #289006 was flaky 560d2d9

[kibanamachine]

Starting backport for target branches: 8.x

https://github.com/elastic/kibana/actions/runs/14448551264

[kibanamachine]

💚 All backports created successfully

Status	Branch	Result
✅	8.x

Note: Successful backport PRs will be merged automatically after passing CI.

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