[9.1] [CI] Use process.uptime() for FTR duration (elastic#242354) (elastic#242533)

# Backport

This will backport the following commits from `main` to `9.1`:
- [[CI] Use process.uptime() for FTR duration
(elastic#242354)](elastic#242354)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Dario
Gieselaar","email":"dario.gieselaar@elastic.co"},"sourceCommit":{"committedDate":"2025-11-11T12:19:51Z","message":"[CI]
Use process.uptime() for FTR duration (elastic#242354)\n\nCurrently for test
duration, we track the time between when the tests\nare starting until
the tests finish, but this ignores Elasticsearch and\nKibana start
times. This is a 2-3m overhead which leads to inefficient\nbalancing of
tests. This PR uses process.uptime() instead, which is a\nmore accurate
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Use process.uptime() for FTR
duration","number":242354,"url":"https://github.com/elastic/kibana/pull/242354","mergeCommit":{"message":"[CI]
Use process.uptime() for FTR duration (elastic#242354)\n\nCurrently for test
duration, we track the time between when the tests\nare starting until
the tests finish, but this ignores Elasticsearch and\nKibana start
times. This is a 2-3m overhead which leads to inefficient\nbalancing of
tests. This PR uses process.uptime() instead, which is a\nmore accurate
representation of how long it takes to run a
config.","sha":"8a953af813bd6674431154f4eaa94a4b4489eec6"}},"sourceBranch":"main","suggestedTargetBranches":[],"targetPullRequestStates":[{"branch":"main","label":"v9.3.0","branchLabelMappingKey":"^v9.3.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/242354","number":242354,"mergeCommit":{"message":"[CI]
Use process.uptime() for FTR duration (elastic#242354)\n\nCurrently for test
duration, we track the time between when the tests\nare starting until
the tests finish, but this ignores Elasticsearch and\nKibana start
times. This is a 2-3m overhead which leads to inefficient\nbalancing of
tests. This PR uses process.uptime() instead, which is a\nmore accurate
representation of how long it takes to run a
config.","sha":"8a953af813bd6674431154f4eaa94a4b4489eec6"}}]}]
BACKPORT-->

Co-authored-by: Dario Gieselaar <dario.gieselaar@elastic.co>

Author: kibanamachine

.buildkite/pipeline-utils/ci-stats/pick_test_group_run_order.ts

@@ -422,7 +422,7 @@ export async function pickTestGroupRunOrder() {
         queue,
         maxMin: FUNCTIONAL_MAX_MINUTES,
         minimumIsolationMin: FUNCTIONAL_MINIMUM_ISOLATION_MIN,
-        overheadMin: 1.5,
+        overheadMin: 0,
         names,
       })),
     ],

src/platform/packages/shared/kbn-test/src/functional_test_runner/lib/mocha/reporter/ci_stats_ftr_reporter.ts

@@ -62,7 +62,7 @@ export function setupCiStatsFtrTestGroupReporter({
   const start = Date.now();
   const group: CiStatsReportTestsOptions['group'] = {
     startTime: new Date(start).toJSON(),
-    durationMs: 0,
+    durationMs: process.uptime() * 1000,
     type: testGroupType,
     name: Path.relative(REPO_ROOT, config.path),
     result: 'skip',
@@ -136,7 +136,7 @@ export function setupCiStatsFtrTestGroupReporter({
     }
 
     // update the durationMs
-    group.durationMs = Date.now() - startMs;
+    group.durationMs = process.uptime() * 1000;
     group.result = failCount ? 'fail' : passCount ? 'pass' : 'skip';
   });