pulsar: add container-based config discovery support

[martavicentenavarro]

What does this PR do?

Adds config discovery support to the Pulsar integration. When the Datadog Agent detects a container with the pulsar AD identifier, it automatically probes port 8080 and schedules an OpenMetrics check against http://<host>:8080/metrics — no manual conf.yaml needed.

Files changed:

• assets/configuration/spec.yaml — discovery: block with ad_identifiers: [pulsar] and from_ports strategy on port 8080
• datadog_checks/pulsar/config_models/discovery.py — autogenerated candidates() function
• datadog_checks/pulsar/data/auto_conf.yaml — AD identifier registration
• tests/conftest.py — wires get_e2e_discovery_config into dd_environment and adds discovery_config fixture
• tests/test_e2e.py — adds test_e2e_discovery E2E test

Port choice: Port 8080 is Pulsar's standard web service port — the official Docker getting started guide exposes it explicitly (-p 8080:8080) and the broker logs confirm HTTP Service started at http://0.0.0.0:8080.

Motivation

Part of the config discovery rollout (DSCVR-485). Follows the same pattern established by the krakend integration (PR #23963).

[datadog-datadog-prod-us1]

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⚠️ Warnings

🚦 2 Pipeline jobs failed

PR | test / check     

PR | test / test (linux, ubuntu-22.04, pulsar, Pulsar (py3.13-2.9), py3.13-2.9) / Pulsar (py3.13-2.9)-py3.13-2.9     

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