Fix flaky feature context integration tests

[kikoveiga]

What does this PR do?

Makes the concurrent feature-context integration tests use disjoint key namespaces for each writer. The change is applied consistently to the add, modify, and remove scenarios in both FeatureSdkCoreTest and InternalSdkCoreTest.

Motivation

The two Forge-generated maps could independently produce the same key. The expected map was built with Kotlin map addition, which deterministically gives precedence to the second map, while the actual updates run concurrently and can validly complete in either order.

For example, both maps generated the key k in the observed failure. The assertion expected the value from the second map, but the first writer acquired the lock last, so its value correctly won. This made the atomicity test fail even though the production locking behavior was correct.

Using first_ and second_ key prefixes removes this accidental same-key conflict so the tests measure atomic updates rather than nondeterministic last-writer-wins behavior.

Additional Notes

This is a test-only change; production feature-context behavior is unchanged.

Validation:

• reliability core integration-test sources compile
• reliability core ktlint checks pass
• all six affected instrumentation tests pass on an API 37 emulator

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)

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T16:57:19.171087Z	0c8a157	New commits

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[datadog-datadog-prod-us1]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🔄 Datadog retried 2 tests - 2 passed on retry

🔄 Datadog auto-retried 2 jobs - 2 passed on retry

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 71.70% (-0.03%)

_{This comment will be updated automatically if new data arrives.
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