PANA-8612: Add snapshot capture orchestration

[jonathanmos]

What does this PR do?

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.

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).

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

🎯 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: 1ca510f | Docs | View more details | Give us feedback!}

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.82403% with 108 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.31%. Comparing base (2ebd855) to head (1ca510f).

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 ⚠️
...y/internal/composition/CaptureGenerationContext.kt	81.13%	4 Missing and 6 partials ⚠️
...ay/internal/composition/AndroidCaptureExecution.kt	70.00%	4 Missing and 5 partials ⚠️
.../sessionreplay/internal/DefaultRecorderProvider.kt	83.33%	6 Missing and 2 partials ⚠️
...ionreplay/internal/composition/CaptureWorkToken.kt	75.00%	3 Missing and 2 partials ⚠️
...nal/composition/AndroidSnapshotCaptureLifecycle.kt	82.61%	3 Missing and 1 partial ⚠️
...ionreplay/internal/composition/CaptureExecution.kt	70.00%	2 Missing and 1 partial ⚠️
...nreplay/internal/composition/SnapshotProcessing.kt	86.67%	2 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##           jmoskovich/01-sr-new-pipeline    #3722      +/-   ##
=================================================================
+ Coverage                          73.30%   73.31%   +0.01%     
=================================================================
  Files                               1009     1019      +10     
  Lines                              37438    37896     +458     
  Branches                            6515     6598      +83     
=================================================================
+ Hits                               27443    27781     +338     
- Misses                              8116     8186      +70     
- Partials                            1879     1929      +50     

Files with missing lines	Coverage Δ
...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%)	⬆️
...nreplay/internal/composition/SnapshotProcessing.kt	86.67% <86.67%> (ø)
...ionreplay/internal/composition/CaptureExecution.kt	70.00% <70.00%> (ø)
...nal/composition/AndroidSnapshotCaptureLifecycle.kt	82.61% <82.61%> (ø)
...ionreplay/internal/composition/CaptureWorkToken.kt	75.00% <75.00%> (ø)
.../sessionreplay/internal/DefaultRecorderProvider.kt	91.28% <83.33%> (-3.35%)	⬇️
...ay/internal/composition/AndroidCaptureExecution.kt	70.00% <70.00%> (ø)
...y/internal/composition/CaptureGenerationContext.kt	81.13% <81.13%> (ø)
... and 3 more

... and 39 files with indirect coverage changes

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