Move experimental configureReadReplication from ctx.storage to ctx.

[jtolio]

Before read replication becomes generally available, make the API more friendly by moving configureReadReplication up. Logically, read replication is more a property of the DO itself than the storage subsystem.

Should be retargeted at main once #6663 is merged

[ask-bonk]

This PR is clean. Let me summarize my analysis:

1. C++ change: Removes configureReadReplication from DurableObjectStorage's JSG registration, adds it to DurableObjectState with a thin wrapper that delegates to the underlying storage. The C++ method on DurableObjectStorage is preserved (not deleted), only the JS binding is moved.

2. Backward compatibility: Not a concern. The replicaRouting compat flag is $experimental, so this API hasn't been exposed in any stable release. Moving it before GA is exactly the right time.

3. Safety: The JSG_REQUIRE_NONNULL(storage, ...) guard is correct since storage is kj::Maybe. The delegation with kj::mv(options) is proper for the struct parameter.

4. Type snapshots: Correctly reflect the move - configureReadReplication added to DurableObjectState, removed from DurableObjectStorage, only in experimental/ (not latest/).

5. No new issues found: The code is a straightforward, well-structured API move.

LGTM

github run

[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 129 skipped benchmarks¹

---

_{Comparing jolio/move-config-read-replication (3a820d2) with jolio/add-ctx-primaryStub (4e7ffab)²}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on jolio/add-ctx-primaryStub (82d96dc) during the generation of this report, so dce322d was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 25 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (jolio/add-ctx-primaryStub@82d96dc). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/workerd/api/actor-state.c++	0.00%	25 Missing ⚠️

Additional details and impacted files

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##             jolio/add-ctx-primaryStub    #6649   +/-   ##
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  Files                                ?      405           
  Lines                                ?   115976           
  Branches                             ?    19409           
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  Hits                                 ?    77133           
  Misses                               ?    27265           
  Partials                             ?    11578           

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