test(instr-document-load): fix test to allow missing network span events

[trentm]

The change in open-telemetry/opentelemetry-js#4486
means that a addSpanNetworkEvent() in v1.24.0 and
later might get dropped -- if its time value is before the fetchStart time.
Typically this happens if the event time value is 0.

[trentm]

This should fix the browser-test failure on #2091

[trentm]

This was written to have the test pass with sdk-trace-web versions before and after 1.24.0 where the change in behaviour happened, because instr-documentation-load has this dep: "@opentelemetry/sdk-trace-web": "^1.15.0",.

to test it

npm ci --ignore-scripts
cd plugins/web/opentelemetry-instrumentation-document-load
npm run compile
npm run test:browser

Then test with the newer sdk-trace-web:

npm install --no-save @opentelemetry/sdk-trace-web@1.24.0
npm run test:browser

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.35%. Comparing base (dfb2dff) to head (c7e9980).
Report is 68 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2145      +/-   ##
==========================================
- Coverage   90.97%   90.35%   -0.63%     
==========================================
  Files         146      147       +1     
  Lines        7492     7679     +187     
  Branches     1502     1575      +73     
==========================================
+ Hits         6816     6938     +122     
- Misses        676      741      +65     

see 10 files with indirect coverage changes

[JamieDanielson]

Thanks for picking this up so quickly! This looks like a better solution than what I was thinking, which was just to set the unloadEventStart and unloadEventEnd to 1571078170306 (one tick higher than fetchStart)