[performance] Disable telemetry for journey by default (#148915)

## Summary

I noticed some noise in [Performance
dashboard](dd0473ac-826f-5621-9a10-25319700326e?_g=(filters:!(),refreshInterval:(pause:!t,value:0),time:(from:now-24h%2Fh,to:now)))
and think it is better to disable Telemetry for journeys by default.

We use it to report performance events and this PR enables it in the
performance pipeline via env variable `PERFORMANCE_ENABLE_TELEMETRY`.
For other pipelines (PRs,
[performance-data-set-extraction](https://buildkite.com/elastic/kibana-performance-data-set-extraction))
running on regular workers or local troubleshooting there is no much
value to collect inconsistent values.

.buildkite/pipelines/performance/daily.yml

@@ -15,6 +15,8 @@ steps:
 
   - label: '💪 Performance Tests with Playwright config'
     command: .buildkite/scripts/steps/functional/performance_playwright.sh
+    env:
+      PERFORMANCE_ENABLE_TELEMETRY: true
     agents:
       queue: kb-static-ubuntu
     depends_on: build

packages/kbn-journeys/journey/journey_ftr_config.ts

@@ -46,6 +46,9 @@ export function makeFtrConfigProvider(
       throw new Error('invalid GITHUB_PR_NUMBER environment variable');
     }
 
+    // Set variable to collect performance events using EBT
+    const enableTelemetry = !!process.env.PERFORMANCE_ENABLE_TELEMETRY;
+
     const telemetryLabels: Record<string, string | boolean | undefined | number> = {
       branch: process.env.BUILDKITE_BRANCH,
       ciBuildId: process.env.BUILDKITE_BUILD_ID,
@@ -86,7 +89,7 @@ export function makeFtrConfigProvider(
 
         serverArgs: [
           ...baseConfig.kbnTestServer.serverArgs,
-          `--telemetry.optIn=${process.env.TEST_PERFORMANCE_PHASE === 'TEST'}`,
+          `--telemetry.optIn=${enableTelemetry && process.env.TEST_PERFORMANCE_PHASE === 'TEST'}`,
           `--telemetry.labels=${JSON.stringify(telemetryLabels)}`,
           '--csp.strict=false',
           '--csp.warnLegacyBrowsers=false',