feat: basic metrics, separate from indexer-rs metrics

[hopeyen]

Description

Added metrics for response time for file requests and Number of bytes transferred per request per file.

• Response Time: Average response time for file requests.
• Throughput: Number of requests handled per unit of time (e.g., requests per second). IndexerServiceMetrics has request counter, the metrics can be built from that
• Error Rate: Percentage of requests resulting in errors. Failure count is tracked by IndexerServiceMetrics
• Data Transfer Efficiency: Amount of data successfully transferred versus requested.
• Uptime and Availability: Percentage of time the server is operational and accessible. Should be tracked by infra
• Request Distribution: Distribution of requests across different files. This can be built from query counter

Issue link (if applicable)

resolves #24

Checklist

• Are tests up-to-date with the new changes?
• Are docs up-to-date with the new changes? (Open PR on docs repo if necessary)

[github-actions]

Pull Request Test Coverage Report for Build 8345184095

Details

• 0 of 67 (0.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
file-service/src/main.rs	0	1	0.0%
file-service/src/file_server/range.rs	0	2	0.0%
file-service/src/file_server/mod.rs	0	4	0.0%
file-service/src/metrics.rs	0	60	0.0%

Totals
Change from base Build 8195152037:	0.0%
Covered Lines:	0
Relevant Lines:	3653

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💛 - Coveralls