Flaky browser test

[legendecas]

I've seen several times of these kinds of random CI failures.

Links:

• https://github.com/open-telemetry/opentelemetry-js/runs/5647907182?check_suite_focus=true
• https://github.com/open-telemetry/opentelemetry-js/runs/5648434572?check_suite_focus=true (chore(deps): update commitlint monorepo (major) - autoclosed #2745)

1) should debug info that injecting headers was skipped
     fetch when request is successful when propagateTraceHeaderCorsUrls does NOT MATCH
     AssertionError: undefined === 'headers inject skipped due to CORS policy'
    at Context.eval (webpack-internal:///./test/fetch.test.ts:385:24)

[legendecas]

Case 2:

1) should fallback to getEntries
     fetch when PerformanceObserver is undefined
     TypeError: Cannot read properties of undefined (reading '0')
    at Context.eval (webpack-internal:///./test/fetch.test.ts:547:43)

Links:

• https://github.com/open-telemetry/opentelemetry-js/runs/5768068153?check_suite_focus=true (fix(sdk-metrics-base): coerce histogram boundaries to be implicit Infinity #2859)

[pichlermarc]

Case 3:

1) should create a span with correct root span
     fetch when request is successful
     TypeError: Cannot read properties of undefined (reading '0')
    at Context.eval (webpack-internal:///./test/fetch.test.ts:254:43)

2) should create a span for preflight request
     fetch when request is successful
     TypeError: Cannot read properties of undefined (reading '0')
    at Context.eval (webpack-internal:///./test/fetch.test.ts:295:43)

https://github.com/open-telemetry/opentelemetry-js/runs/5875767862?check_suite_focus=true (main)

I noticed as well that some instrumentation-fetch tests have been failing while working on some of my previous PRs. I hope I have not introduced additional flakiness in the last one (#2871).

[Flarna]

We should really aim to get some browser experts into the team. It's not just about flaky tests, also the dependencies (see #2187) to e.g. webpack/karma (and related plugins) are not update since quite a while.