Configure dynamic historical sync ranges in indexer_metrics_collector

[francisdouglas-ux]

Problem & Goal

Enable indexer_metrics_collector to accept dynamic start/end ledger values for custom historical event imports.

Context & Components

• Target Repository: escrow-backend
• Module/Component: indexer_metrics_collector (Poller performance telemetry tracker)

Implementation Details

1. Review the existing codebase inside the escrow-backend directory.
2. Locate the source files relating to indexer_metrics_collector.
3. Implement the feature logic/validation rules step-by-step.
4. Ensure code conforms to codebase patterns (lints, formats, types).

Verification & Testing Requirements

• Validation check: Assert correct block event counts are indexed.
• Add comprehensive test cases matching these validation requirements.
• Ensure all other existing project tests continue to compile and pass.

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Note: This issue is completely self-contained and does not block or require any other issues to be resolved.

[Awosdot]

@Awosdot has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Please assign this to me, I can take care of it

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[Tekh134]

@Tekh134 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi maintainer,

Build and checks are all passing on my end.
I can take this issue and fix it.
Kindly assign me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Tekh134 to this issue.

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[drips-wave]

This issue has been completed by @Tekh134 as part of the Stellar Wave Program's 8th Wave 🥳

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