refacto: make async persisting logic more readable and maintainable

[GhilesA]

PR Summary

use a ScheduledExecutorService to handle the background periodic logic safely cancel, wait for completion and close the threads and executor using its api
remove Thread::sleep from the code

@jonenst some questions are still remaining, can you provide some background info on the TODOs and FIXME ?

[Copilot]

Pull request overview

This PR refactors the asynchronous result persistence logic to improve readability and maintainability by replacing manual thread management with ScheduledExecutorService. The refactoring eliminates Thread.sleep() calls and introduces better structured components for batch processing and polling.

Changes:

• Replaced SensitivityResultWriterPersisted with SensitivityResultPersistedWriter, refactoring from manual thread management to ScheduledExecutorService-based scheduling
• Introduced new components: BatchAsyncPoller for generic batch polling logic, ExecutorsProviderService for thread pool creation, and BatchAsyncPollerFactory for poller instantiation
• Updated SensitivityAnalysisWorkerService to use the new writer with simplified async completion handling

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
src/main/java/org/gridsuite/sensitivityanalysis/server/util/SensitivityResultPersistedWriter.java	New implementation replacing the old writer, using ScheduledExecutorService and delegating to BatchAsyncPoller instances
src/main/java/org/gridsuite/sensitivityanalysis/server/util/BatchAsyncPoller.java	Core component for batch polling and periodic data draining with proper cancellation and completion handling
src/main/java/org/gridsuite/sensitivityanalysis/server/util/ExecutorsProviderService.java	Spring service providing configured ScheduledExecutorService instances with custom thread naming
src/main/java/org/gridsuite/sensitivityanalysis/server/util/BatchAsyncPollerFactory.java	Factory for creating BatchAsyncPoller instances (should be marked as Spring service)
src/main/java/org/gridsuite/sensitivityanalysis/server/service/SensitivityAnalysisWorkerService.java	Integrates the new writer with updated async completion and error handling logic
src/test/java/org/gridsuite/sensitivityanalysis/server/util/SensitivityResultPersistedWriterTest.java	Unit tests for the new writer implementation
src/test/java/org/gridsuite/sensitivityanalysis/server/util/BatchAsyncPollerTest.java	Comprehensive unit tests for the batch poller
src/test/java/org/gridsuite/sensitivityanalysis/server/util/ExecutorsProviderServiceTest.java	Unit tests for the executor service provider
src/main/java/org/gridsuite/sensitivityanalysis/server/util/SensitivityResultWriterPersisted.java	Deleted - replaced by SensitivityResultPersistedWriter
src/test/java/org/gridsuite/sensitivityanalysis/server/util/SensitivityResultWriterPersistedTest.java	Deleted - replaced by SensitivityResultPersistedWriterTest

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
95.5% Coverage on New Code
0.0% Duplication on New Code

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