Show distinct set of URLs for pages listed in the Behavior Top Pages panel

For path fragments, that is explored as a separate enhancement in Update top pages panel under the behavior dashb... (#420898)

Summary

In implementing Deeplink URLs presented as Top Pages in the Beh... (#406815 - closed), we ended up breaking the "Top pages" panel in the Behavior dashboard, splitting out results because the deep links were including page fragments, showing the same URL as multiple line items under "Top pages".

Problem

This is confusing to a user because if you expect your homepage, e.g. /, to be the top page, it shouldn't show up multiple times in the visualization.

Proposal

Use a different dimension when deep-linking URLs in the Top Pages visualization, such that each URL shows up only once, resulting in a list of distinct pages that are sorted from most page views to fewest.

Example

Page URLPath	Views
content/voice-and-tone	180
other-page/	75
/	10

Implementation plan

Update CubeJS TrackedEvents.js schema (also in analytics-stack):

• add new baseUrl dimension which we can combine with path to create a link href:

    baseUrl: {
      sql: `CONCAT(page_urlscheme, '://', page_urlhost, IF(page_urlport IS NOT NULL AND page_urlport != '', ':', ''), page_urlport)`,
      type: `string`,
    },

Modify top_pages.yml visualization:

• query for baseUrl dimension instead of pageUrl (this means results will no longer be split by full URL, and will be split by path + baseUrl. The same path over different baseUrl would result in separate rows in the dashboard, which seems correct)
• links href becomes array of baseUrl and pageUrlpath

Update JSON schema:

• allow href to be an array of multiple fields, e.g.

"href": {
          "oneOf": [
            {
              "type": "string"
            },
            {
              "type": "array",
              "items": {
                "type": "string"
              }
            }
          ]
        }

Update cube_analytics.js:

• modify link dimensions code to accept an array of dimensions as well as a single dimension
• concat multiple dimensions to create an href

Update tests, and docs.