fix: perf relative traces and values

[vigneshshanmugam]

• fix Improve mapping for additional metrics #303
• Relative traces and metrics are grouped under two keys now to provide clear distinction.
• Grouped all traces under browser.relative_trace to keep the mapping similar and these traces are mark or measure events with start and end time denoting the time when particular event (LCP, FCP, etc) occurred during the waterfall.
• All distinct values like FCP, LCP, CLS, etc are grouped under browser.experience.<metric-name> to keep the querying easier in the UI and useful for displaying values in step detail page.

Relative trace events

{
  "type": "journey/metrics",
  "@timestamp": 1623300251603855.2,
  "journey": {
    "name": "check if title is present",
    "id": "check if title is present"
  },
  "root_fields": {
    "browser": {
      "relative_trace": {
        "name": "firstContentfulPaint",
        "type": "mark",
        "start": {
          "us": 142089104934
        }
      }
    },
  }
}

{
  "type": "journey/metrics",
  "journey": {
    "name": "inline",
    "id": "inline"
  },
  "root_fields": {
    "browser": {
      "relative_trace": {
        "name": "widget_core:widget_loaded",
        "type": "measure",
        "start": {
          "us": 142095075042
        },
        "end": {
          "us": 142095312098
        }
      }
    },
  }
}

Experience metrics

{
  "type": "journey/metrics",
  "@timestamp": 1623300251603949.5,
  "journey": {
    "name": "check if title is present",
    "id": "check if title is present"
  },
  "root_fields": {
    "browser": {
      "experience": {
        "cls": 0,
        "fcp": {
          "us": 189382
        },
        "lcp": {
          "us": 189382
        },
        "dcl": {
          "us": 209052
        },
        "load": {
          "us": 209115
        }
      }
    },
}

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Build stats

• Build Cause: Pull request #306 updated

• Start Time: 2021-06-14T17:21:46.528+0000

• Duration: 13 min 58 sec

• Commit: d3fab05

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Failed	0
Passed	109
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Total	109

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[vigneshshanmugam]

all CLS relative trace events will be added as part of the work in #301

[andrewvc]

Found some more missing units, otherwise got. Looking better!

[andrewvc]

LGTM, so much cleaner with easy to read units :)