[RUMF-766] prevent request duration override by wrong matching timing

[bcaudan]

Motivation

Quick fix to see if demo website shorter browser spans could be related to wrong timing association.
Since TAO is not enabled on shopist, we should observe a duration increase for RUM fetch events.

Changes

Do not consider invalid or incomplete timing in match request timing.

Testing

unit test, manual tests on DD + demo

Next steps

if hypothesis is confirmed, discuss proper strategies.

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I have gone over the contributing documentation.

[BenoitZugmeyer]

LGTM

[codecov-io]

Codecov Report

Merging #604 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #604      +/-   ##
==========================================
+ Coverage   88.83%   88.85%   +0.01%     
==========================================
  Files          54       54              
  Lines        2490     2503      +13     
  Branches      540      541       +1     
==========================================
+ Hits         2212     2224      +12     
- Misses        278      279       +1     

Impacted Files	Coverage Δ
...rumEventsCollection/resource/matchRequestTiming.ts	94.11% <100.00%> (ø)
...main/rumEventsCollection/resource/resourceUtils.ts	96.42% <100.00%> (+0.42%)	⬆️
packages/rum/test/fixtures.ts	100.00% <100.00%> (ø)
packages/rum/src/browser/performanceCollection.ts	64.28% <0.00%> (-1.43%)	⬇️

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