Add generic performance metrics support to Allure reports

[formaceft-93]

The main use case of the feature is performance measurements, but the format is intentionally not tied to Allure’s own benchmark phases, so other projects can publish their own numeric metrics through perf.json.
The report now reads explicit metric samples, adapts the current allure-perf-metrics.json format, and can also flatten arbitrary numeric JSON values into metric keys. Metrics are stored separately from test results, exported to widgets/metrics.json, attached as raw input for audit/debugging, and included in report history as stable key -> value pairs for trend views.
On the UI side, Awesome gets a dedicated Metrics section with grouped summary rows, current values, deltas, trends, and a selected history metric. Dashboard gets a compact metrics widget. The internal perf writer also emits an allure.total summary metric so the default history view can show an end-to-end report generation number instead of a project-specific phase.

Example perf.json:

{
  "version": 1,
  "name": "Build performance",
  "display": {
    "historyMetricKey": "build.total.avgMs"
  },
  "metrics": [
    {
      "key": "build.total.avgMs",
      "name": "Build total",
      "group": "Build",
      "value": 12450,
      "unit": "ms",
      "better": "lower"
    }
  ]
}

[github-actions]

Allure Report Summary

	Name	Duration	Stats	New	Flaky	Retry	Report
	Allure 3 Report	41m 53s	9947    15    21	81	0	33	View
	My Dashboard	41m 53s	9947    15    21	81	0	33	View

[github-actions]

Allure perf metrics

Generated at: 2026-06-18T10:12:30.527Z

Phase	Count	Total	Avg	Min	Max
restoreState.total	1	2762.1 ms	2762.1 ms	2762.1 ms	2762.1 ms
restoreState.dump	3	2761.6 ms	920.5 ms	874.7 ms	948.6 ms
restoreState.attachments	3	2174.2 ms	724.7 ms	709.1 ms	739.2 ms
restoreState.storeRestore	3	170.9 ms	57.0 ms	50.8 ms	64.8 ms
generate.total	1	697400.3 ms	697400.3 ms	697400.3 ms	697400.3 ms
generate.plugins.done	1	8703.8 ms	8703.8 ms	8703.8 ms	8703.8 ms
publish.upload.total	1	392721.1 ms	392721.1 ms	392721.1 ms	392721.1 ms
summary.generate	2	14.6 ms	7.3 ms	7.0 ms	7.6 ms
generate.plugin.done.agent	1	0.3 ms	0.3 ms	0.3 ms	0.3 ms
generate.plugin.done.awesome	1	6993.9 ms	6993.9 ms	6993.9 ms	6993.9 ms
generate.plugin.done.dashboard	1	1065.2 ms	1065.2 ms	1065.2 ms	1065.2 ms
generate.plugin.done.log	1	3.7 ms	3.7 ms	3.7 ms	3.7 ms
generate.plugin.done.testops	1	640.1 ms	640.1 ms	640.1 ms	640.1 ms
publish.upload.plugin.awesome	1	383185.2 ms	383185.2 ms	383185.2 ms	383185.2 ms
publish.upload.plugin.dashboard	1	2165.8 ms	2165.8 ms	2165.8 ms	2165.8 ms

Artifacts: allure-perf-metrics