Add http.Servers timeouts

[simonlechner]

This PR adds timeouts to the standalone pprof and metrics http.Servers.

[Copilot]

Pull request overview

This PR refactors the standalone pprof and metrics HTTP servers to use explicit http.Server instances with configured timeouts, and adds tests around the new server constructors and endpoint availability.

Changes:

• Replace http.ListenAndServe calls with configured http.Server instances for pprof and metrics endpoints.
• Add newPProfServer / newMetricsServer helpers to centralize server configuration (address + timeouts).
• Add/extend tests to validate timeouts and to confirm key endpoints are served.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
debug/flags.go	Introduces newPProfServer and uses it from StartPProf to apply server timeouts.
debug/flags_test.go	Adds tests for newPProfServer and verifies pprof/metrics endpoints are reachable.
cmd/sonicd/metrics/flags.go	Introduces newMetricsServer and uses it from setupMetricsServer to apply server timeouts.
cmd/sonicd/metrics/flags_test.go	Adds a test ensuring newMetricsServer sets expected defaults (addr/handler/timeouts).

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[codecov]

Codecov Report

❌ Patch coverage is 91.30435% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cmd/sonicd/metrics/flags.go	92.85%	0 Missing and 1 partial ⚠️
debug/flags.go	88.88%	0 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
cmd/sonicd/metrics/flags.go	26.08% <92.85%> (+11.08%)	⬆️
debug/flags.go	56.16% <88.88%> (+14.62%)	⬆️

... and 9 files with indirect coverage changes

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[thaarok]

I am not sure if tests TestNewPProfServer_HasTimeouts and TestNewMetricsServer_SetsDefaultValues are meaningful, since they only tests assigning into a structure, but if it is required by the coverage requirements...