♻️ [RUM-6188] Use performanceObserver for first input and event entries

[amortemousque]

Motivation

Following the introduction of performanceObservable to move away from performanceCollection: PR
Let use performanceObservable for first input and event entries.

Changes

• Remove long-task and event entries from performanceCollection
• Isolate firstInputPolyfill.ts in its own file
• Use perfomanceObservable in trackFirstInput
• Use perfomanceObservable in trackInteractionToNextPaint

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 48.21429% with 29 lines in your changes missing coverage. Please review.

Project coverage is 93.36%. Comparing base (5e00489) to head (aee8c5b).

Files with missing lines	Patch %	Lines
...ackages/rum-core/src/browser/firstInputPolyfill.ts	0.00%	25 Missing ⚠️
...ages/rum-core/src/browser/performanceObservable.ts	42.85%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2995      +/-   ##
==========================================
- Coverage   93.38%   93.36%   -0.02%     
==========================================
  Files         275      276       +1     
  Lines        7639     7647       +8     
  Branches     1716     1716              
==========================================
+ Hits         7134     7140       +6     
- Misses        505      507       +2     

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[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	161.83 KiB	161.95 KiB	125 B	+0.08%	✅
Logs	56.03 KiB	56.03 KiB	0 B	0.00%	✅
Rum Slim	110.40 KiB	110.52 KiB	125 B	+0.11%	✅
Worker	25.21 KiB	25.21 KiB	0 B	0.00%	✅

🚀 CPU Performance

Action Name	Base Average Cpu Time (ms)	Local Average Cpu Time (ms)	𝚫
addglobalcontext	0.002	0.002	-0.000
addaction	0.034	0.040	0.006
addtiming	0.001	0.001	-0.000
adderror	0.032	0.032	-0.000
startstopsessionreplayrecording	0.868	0.931	0.063
startview	1.006	0.972	-0.034
logmessage	0.019	0.021	0.002

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	9.39 KiB	7.96 KiB	-1465 B
addaction	39.10 KiB	39.96 KiB	879 B
addtiming	7.31 KiB	6.46 KiB	-864 B
adderror	44.63 KiB	45.20 KiB	592 B
startstopsessionreplayrecording	5.83 KiB	4.54 KiB	-1323 B
startview	356.31 KiB	408.51 KiB	52.20 KiB
logmessage	40.29 KiB	40.76 KiB	478 B

🔗 RealWorld

[BenoitZugmeyer]

NIT: you could remove the condition on entryType below