♻️ [RUMF-1440] improve feature flag collection implementation

[amortemousque]

Motivation

Extracting feature flag management to a dedicated component.

Changes

• Remove feature flag logic from trackViews
• Create featureFlagContexts
• Use featureFlagContexts in viewCollection and errorCollection

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

Merging #1839 (d4e32e4) into main (329ff34) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1839      +/-   ##
==========================================
+ Coverage   93.03%   93.12%   +0.09%     
==========================================
  Files         131      132       +1     
  Lines        5081     5093      +12     
  Branches     1138     1139       +1     
==========================================
+ Hits         4727     4743      +16     
+ Misses        354      350       -4     

Impacted Files	Coverage Δ
...kages/rum-core/src/domain/contexts/viewContexts.ts	100.00% <ø> (ø)
.../src/domain/rumEventsCollection/view/trackViews.ts	100.00% <ø> (ø)
packages/rum-core/src/boot/startRum.ts	86.66% <100.00%> (+0.62%)	⬆️
...rum-core/src/domain/contexts/featureFlagContext.ts	100.00% <100.00%> (ø)
...omain/rumEventsCollection/error/errorCollection.ts	100.00% <100.00%> (ø)
.../domain/rumEventsCollection/view/viewCollection.ts	100.00% <100.00%> (ø)
...rum-core/src/domain/contexts/foregroundContexts.ts	96.92% <0.00%> (+6.15%)	⬆️

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