Add a new field "xdm:path" to summary-metrics field group

### Summary

Since onboarding, a request for an additional field "path" has been requested to be added to the xdm schema.

This will allow us to re-utilize URL to be host + path.

This will enable customers to be able to join their cdn logs to their other existing datasets more easily on the URL

### Implementation

Field group: components/fieldgroups/summary-metrics/cdn-requests-summary.schema.json
Extends: https://ns.adobe.com/xdm/classes/summarymetrics

### Related

Jira: AN-458308

Open components/fieldgroups/summary-metrics/cdn-requests-summary.schema.json and review how the existing fields are defined under the summarymetrics extension. Add the requested xdm:path field to this field group, then verify the schema still represents the host-plus-path URL use case described in the issue.

Written by the indexing model from the issue text.