feat: add HTTP readiness latency benchmark

[jim-junior]

This PR adds an HTTP readiness latency benchmark adapter.

The benchmark measures how long a container takes to become ready to serve HTTP requests. Measurement begins immediately before the OCI start command is invoked and ends when the container returns its first HTTP 200 OK response.

How It Works

The adapter uses the CLI-based execution path with nerdctl instead of the Go containerd API.

The benchmark performs the following steps:

1. Creates the container.
2. Starts an HTTP readiness probe in a goroutine.
3. Records the start time immediately before invoking the container start command.
4. Continuously sends HTTP GET requests to the container URL.
5. Waits until the first HTTP 200 OK response is received.
6. Records the readiness latency and total number of attempts.

Only HTTP 200 OK is considered a successful readiness response.

The probe ignores:

• Connection refused errors
• Connection reset errors
• Request timeouts
• HTTP 4xx responses
• HTTP 5xx responses
• Any other non-200 HTTP response

Container Images

Runtime	Image
runc	docker.io/library/nginx:latest
Kata Containers	docker.io/library/nginx:latest
gVisor	docker.io/library/nginx:latest
urunc	harbor.nbfc.io/nubificus/urunc/nginx-qemu-unikraft-initrd:latest

Readiness Latency Definition

HTTP readiness latency = time of first HTTP 200 response - time immediately before the OCI start command

This represents the time taken for the containerized HTTP server to become available after the runtime start operation is invoked.

Output Format

The readiness data is recorded in the adapter's Wait Ready stage.

Example:

{
  "attempts": 482, // Number of HTTP requests made before receiving the first 200 OK response
  "end": "2026-08-02T15:45:24.768593448+03:00",
  "latency": 1893693110,
  "latency_ms": 1893.693,
  "readiness_latency": 1893693110,
  "readiness_latency_ms": 1893.693,
  "ready_at": "2026-08-02T15:45:24.768593448+03:00",
  "start": "2026-08-02T15:45:22.874900338+03:00",
  "status_code": 200,
  "url": "http://127.0.0.1:8082/"
}