⚡️[RUM-3570] Batch the records for 16ms minimum before processing them

[amortemousque]

Motivation

When recording for Session Replay, MutationRecord objects are batched together (see mutationBatch), then deduplicated on processing (ex: here).

When the same mutation happens continuously on the same element, for example with JS-driven animations, a lot of MutationRecords can be notified by the browser in a very short amount of time, which can significantly inflate the data sent to Datadog, and have a performance impact both on the recorder side and on the player side (see below). Those mutations could be deduplicated if they were batched together.

Changes

Batch the records for 16ms minimum before processing them

Testing

• [x] Local
• [ ] Staging
• [x] Unit
• [ ] End to end

---

I have gone over the contributing documentation.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 93.65%. Comparing base (b839f8c) to head (28d38d9).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2807 +/- ## ======================================= Coverage 93.65% 93.65% ======================================= Files 243 243 Lines 7140 7143 +3 Branches 1599 1599 ======================================= + Hits 6687 6690 +3 Misses 453 453 ```

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[cit-pr-commenter[bot]]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	159.49 KiB	159.55 KiB	62 B	+0.04%	✅
Logs	58.02 KiB	58.02 KiB	0 B	0.00%	✅
Rum Slim	108.07 KiB	108.07 KiB	0 B	0.00%	✅
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 | 0.050 | 0.042 | -0.007 | | adderror | 0.052 | 0.034 | -0.017 | | addtiming | 0.001 | 0.001 | -0.001 | | startview | 1.427 | 0.999 | -0.428 | | startstopsessionreplayrecording | 1.077 | 0.825 | -0.252 | | logmessage | 0.007 | 0.019 | 0.012 |

🧠 Memory Performance

| Action Name | Base Consumption Memory (bytes) | Local Consumption Memory (bytes) | 𝚫 (bytes) | | --- | --- | --- | --- | | addglobalcontext | 19.58 KiB | 18.83 KiB | -766 B | | addaction | 68.97 KiB | 68.36 KiB | -632 B | | adderror | 83.18 KiB | 85.19 KiB | 2.00 KiB | | addtiming | 17.24 KiB | 17.05 KiB | -193 B | | startview | 313.58 KiB | 317.81 KiB | 4.22 KiB | | startstopsessionreplayrecording | 11.51 KiB | 12.38 KiB | 890 B | | logmessage | 64.11 KiB | 67.06 KiB | 2.95 KiB |