PANA-8612: Add snapshot capture orchestration

[jonathanmos]

What does this PR do?

Second pr for the new pipeline.

Adds the orchestration layer for the composition capture pipeline: SnapshotCaptureOrchestrator serializes snapshot "generations" end-to-end (traversal, async processing, expiry, handoff), coalescing overlapping capture requests into one follow-up and tracking a CaptureChangeset describing what changed (accepted for now, not yet consumed by traversal). Wires this and its supporting pieces (generation/time-budget primitives, Android scheduling and lifecycle glue, the completion queue) into DefaultRecorderProvider.

Also fixes a gap in that wiring: DefaultRecorderProvider computed the heatmap identifier registry unconditionally but only forwarded it to the legacy recorder, so enabling setHeatmapsEnabled(true) together with setCompositionTreeRecordingEnabled(true) silently dropped heatmap data with no signal to the caller. It now logs a WARN/Target.USER message for that combination, and setCompositionTreeRecordingEnabled's KDoc documents the incompatibility.

Motivation

Continues the new composition-tree capture pipeline (stacked on PANA-8500). The recorder and processing pieces already existed; this PR adds the piece that actually drives a capture end-to-end — deciding when a generation starts, enforcing its time budget, serializing overlapping requests, and handing the result off — while keeping platform callback wiring and the real view-traversal producer out of scope for later workstreams (CompositionCapturePipeline's producer is still a test seam here). Because there is no traversal implementation yet, compositionTreeRecordingEnabled stays disabled by default and reachable only through the existing @ExperimentalSessionReplayApi; the heatmap warning exists so that gap doesn't surface as a silent feature regression in the meantime.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[datadog-official]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🔄 Datadog retried 1 test - 1 passed on retry

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 72.82% (+0.00%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 50400d0 | Docs | View more details | Give us feedback!}

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.80127% with 105 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.35%. Comparing base (2ebd855) to head (50400d0).
⚠️ Report is 1 commits behind head on feature/sr-new-pipeline.

Files with missing lines	Patch %	Lines
...nternal/composition/SnapshotCaptureOrchestrator.kt	80.74%	10 Missing and 16 partials ⚠️
...ay/internal/composition/SnapshotCompletionQueue.kt	63.08%	13 Missing and 11 partials ⚠️
...lay/internal/composition/CompositionDrawSignals.kt	64.58%	12 Missing and 5 partials ⚠️
...ay/internal/composition/AndroidCaptureExecution.kt	70.00%	4 Missing and 5 partials ⚠️
.../sessionreplay/internal/DefaultRecorderProvider.kt	84.91%	6 Missing and 2 partials ⚠️
...y/internal/composition/CaptureGenerationContext.kt	87.27%	3 Missing and 4 partials ⚠️
...ionreplay/internal/composition/CaptureWorkToken.kt	75.00%	3 Missing and 2 partials ⚠️
...nal/composition/AndroidSnapshotCaptureLifecycle.kt	82.61%	3 Missing and 1 partial ⚠️
...onreplay/internal/composition/CaptureTimeBudget.kt	75.00%	1 Missing and 1 partial ⚠️
...nreplay/internal/composition/SnapshotProcessing.kt	86.67%	2 Missing ⚠️
... and 1 more

Additional details and impacted files

@@                     Coverage Diff                     @@
##           feature/sr-new-pipeline    #3722      +/-   ##
===========================================================
+ Coverage                    73.30%   73.35%   +0.04%     
===========================================================
  Files                         1009     1021      +12     
  Lines                        37438    37902     +464     
  Branches                      6515     6599      +84     
===========================================================
+ Hits                         27443    27800     +357     
- Misses                        8116     8183      +67     
- Partials                      1879     1919      +40     

Files with missing lines	Coverage Δ
...ndroid/sessionreplay/SessionReplayConfiguration.kt	97.89% <ø> (-0.02%)	⬇️
...lay/internal/composition/CancellableCaptureWork.kt	100.00% <100.00%> (ø)
...nternal/composition/CaptureSkippedFrameNotifier.kt	100.00% <100.00%> (ø)
...sessionreplay/internal/composition/CapturedTree.kt	90.24% <100.00%> (+0.24%)	⬆️
...internal/composition/CompositionCapturePipeline.kt	100.00% <100.00%> (+54.55%)	⬆️
...onreplay/internal/composition/CaptureScheduling.kt	0.00% <0.00%> (ø)
...onreplay/internal/composition/CaptureTimeBudget.kt	75.00% <75.00%> (ø)
...nreplay/internal/composition/SnapshotProcessing.kt	86.67% <86.67%> (ø)
...nal/composition/AndroidSnapshotCaptureLifecycle.kt	82.61% <82.61%> (ø)
...ionreplay/internal/composition/CaptureWorkToken.kt	75.00% <75.00%> (ø)
... and 6 more

... and 34 files with indirect coverage changes

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[jonathanmos]

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