test(origin): add benchmark for number of http connections

[sambhav-jain-16]

> go test -tags unit -run '^$' -bench BenchmarkTransferBlob -benchtime=3s ./origin/blobclient/ 2>&1
goos: linux
goarch: amd64
pkg: github.com/uber/kraken/origin/blobclient
cpu: AMD EPYC 7B13
BenchmarkTransferBlob/http_unpooled-96                 1051           3143513 ns/op        1334.27 MB/s             0.0009515 conns/op
BenchmarkTransferBlob/https_unpooled-96                 175          20385623 ns/op         205.75 MB/s             6.000 conns/op
     PASS
     ok         github.com/uber/kraken/origin/blobclient        9.446s

[Copilot]

Pull request overview

This PR adds a Go benchmark in origin/blobclient to quantify how many TCP connections are established per TransferBlob call (server-side Accept() count), comparing HTTP vs HTTPS behavior to surface keep-alive/connection reuse differences.

Changes:

• Added a benchmark harness for TransferBlob that uploads a fixed-size blob against a local httptest server.
• Introduced a net.Listener wrapper to count accepted TCP connections and report conns/op as a benchmark metric.

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[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.