✨ [RUM-6565] Capture previous and current rects in CLS attribution data

[sethfowler-datadog]

Motivation

When trying to understand the causes and impact of a Cumulative Layout Shift score, it's often helpful to see how the affected element's position and size has changed.

Changes

This PR adds the capability to capture the previous and current rects associated with layout shifts on supported browsers. The changes build on the standard LayoutShiftAttribution API and the recent changes in rum-events-format which gave us a place to store this data.

Testing

• Local
• Staging
• Unit
• End to end

---

I have gone over the contributing documentation.

[sethfowler-datadog]

The account-related changes here got pulled in by yarn rum-events-format:sync. They're unrelated to the PR, but unfortunately it's hard to avoid pulling them in because of the order in which things got merged into rum-events-format. They'll disappear from the diff if Nicolas merges the PR that motivated them before this one lands, though, so the issue is temporary.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.66%. Comparing base (85baa2b) to head (91ea40a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3269      +/-   ##
==========================================
- Coverage   93.67%   93.66%   -0.01%     
==========================================
  Files         288      288              
  Lines        7607     7613       +6     
  Branches     1735     1739       +4     
==========================================
+ Hits         7126     7131       +5     
- Misses        481      482       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[cit-pr-commenter]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	145.14 KiB	145.51 KiB	378 B	+0.25%	✅
Logs	51.09 KiB	51.09 KiB	0 B	0.00%	✅
Rum Slim	103.94 KiB	104.30 KiB	378 B	+0.36%	✅
Worker	24.50 KiB	24.50 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	0.001
addaction	0.040	0.062	0.022
addtiming	0.001	0.002	0.000
adderror	0.045	0.069	0.024
startstopsessionreplayrecording	0.008	0.014	0.006
startview	0.395	0.450	0.055
logmessage	0.028	0.032	0.004

🧠 Memory Performance

Action Name	Base Consumption Memory (bytes)	Local Consumption Memory (bytes)	𝚫 (bytes)
addglobalcontext	27.77 KiB	29.79 KiB	2.03 KiB
addaction	55.14 KiB	58.69 KiB	3.55 KiB
addtiming	26.47 KiB	25.86 KiB	-631 B
adderror	61.06 KiB	60.10 KiB	-978 B
startstopsessionreplayrecording	28.53 KiB	25.42 KiB	-3186 B
startview	415.29 KiB	418.25 KiB	2.97 KiB
logmessage	57.03 KiB	58.28 KiB	1.25 KiB

🔗 RealWorld