🐛 [RUM-958] Fix performance observable compatibility with old browser version

[amortemousque]

Motivation

Looking at the telemetry, it seems that users still use very old version of Chrome (<75) and Apple Mail which do not support performance observer buffered and type parameters. This PR adds a fallback strategy for these cases using:

• performance observer entryTypes and
• performance.getEntriesByType() for the buffered entries

Changes

Add fallback strategy to createPerformanceObservable

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.65%. Comparing base (30ae145) to head (7f7ac34).
Report is 94 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2850      +/-   ##
==========================================
- Coverage   93.66%   93.65%   -0.01%     
==========================================
  Files         266      266              
  Lines        7573     7582       +9     
  Branches     1683     1687       +4     
==========================================
+ Hits         7093     7101       +8     
- Misses        480      481       +1     

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[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	161.37 KiB	161.57 KiB	205 B	+0.12%	✅
Logs	57.97 KiB	57.97 KiB	0 B	0.00%	✅
Rum Slim	109.89 KiB	110.09 KiB	205 B	+0.18%	✅
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	0.001	-0.000
addaction	0.034	0.032	-0.003
adderror	0.051	0.031	-0.020
addtiming	0.001	0.001	-0.000
startview	1.230	0.916	-0.314
startstopsessionreplayrecording	0.906	0.853	-0.053
logmessage	0.023	0.018	-0.004

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	22.05 KiB	19.88 KiB	-2219 B
addaction	73.70 KiB	73.70 KiB	1 B
adderror	88.13 KiB	86.38 KiB	-1795 B
addtiming	19.17 KiB	18.77 KiB	-408 B
startview	333.58 KiB	352.16 KiB	18.57 KiB
startstopsessionreplayrecording	16.50 KiB	14.20 KiB	-2354 B
logmessage	71.05 KiB	72.07 KiB	1.02 KiB

🔗 RealWorld