New Container: Prometheus

Feature Request: PrometheusContainer

What is the new container you'd like to have?

I'd like to propose a PrometheusContainer for integration testing with Prometheus.

Relevant resources:

• Docker image: https://hub.docker.com/r/prom/prometheus
• Prometheus docs: https://prometheus.io/docs/introduction/overview/

Besides exposing the Prometheus UI/API, it could provide convenience methods to configure scrape targets and rules directly, without requiring users to write and mount a complete prometheus.yml, for example:

prometheus = (
    PrometheusContainer()
    .with_scrape_target("app", app_container, port=8080, metrics_path="/metrics")
    .with_scrape_target("redis", redis_exporter)
)

The container could generate the corresponding prometheus.yml internally while still allowing users to provide a custom configuration file if needed.

Why not just use a generic container for this?

While DockerContainer("prom/prometheus") works, most tests usually need additional setup:

• Configuring scrape targets.
• Providing a Prometheus configuration.
• Waiting until Prometheus is ready to accept requests.
• Reload Prometheus on config change.
• etc.

Other references

A similar idea has already been discussed in the testcontainers-java

No se nombran archivos de implementación ni pruebas. Empieza revisando las implementaciones de contenedores existentes de testcontainers-python y la documentación de Prometheus y la imagen de Docker enlazadas; se considera terminado cuando un PrometheusContainer puede exponer la UI/API, configurar objetivos de scrape o un prometheus.yml personalizado, y admitir las cuestiones de readiness y recarga de configuración descritas en el issue.