✨[RUMF-970] enable buffered PerformanceObserver

[bcaudan]

Motivation

Retrieve largest-contentful-paint, first-input and layout-shift values that could have been emitted before SDK init.

Changes

Remove 'buffered-perf' flag

related PRs:

• ⚗ [RUMF-970] experiment with buffered PerformanceObserver #972
• ⚗ [RUMF-970] Buffered PerformanceObserver: add fallback for older browsers #978

Testing

Manual + DD app

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Merging #995 (2767f6b) into main (d4d05d7) will increase coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #995      +/-   ##
==========================================
+ Coverage   88.83%   88.87%   +0.04%     
==========================================
  Files          84       84              
  Lines        3913     3910       -3     
  Branches      866      865       -1     
==========================================
- Hits         3476     3475       -1     
+ Misses        437      435       -2     

Impacted Files	Coverage Δ
...ages/rum-core/src/browser/performanceCollection.ts	14.00% <0.00%> (+0.40%)	⬆️
packages/core/src/tools/timeUtils.ts	90.90% <0.00%> (-3.04%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d4d05d7...2767f6b. Read the comment docs.