fix(toxiproxy): add Toxiproxy container module

[JonnasFigueiredo]

New Container

Fixes #1104

Adds a ToxiproxyContainer (testcontainers.community.toxiproxy) that wraps Toxiproxy for simulating adverse network conditions — latency, bandwidth limits, connection drops and more — in integration tests. Toxiproxy modules already exist for testcontainers Java, Go and .NET; this brings the same to Python.

What it does

• ToxiproxyContainer exposes the HTTP control API (8474) and a range of proxy ports, and waits on the control API before it's ready.
• create_proxy(name, upstream) routes traffic to an upstream (e.g. "nginx:80" of a container that shares a network) and returns a ToxiproxyProxy whose host/proxy_port you connect through.
• ToxiproxyProxy.add_toxic(...) injects toxics via the control API.
• No extra runtime dependencies — the control API is called over urllib.

Usage

with Network() as network:
    nginx = NginxContainer("nginx:alpine").with_network(network).with_network_aliases("nginx")
    toxiproxy = ToxiproxyContainer().with_network(network)
    with nginx, toxiproxy:
        proxy = toxiproxy.create_proxy("nginx", "nginx:80")
        proxy.add_toxic("latency", {"latency": 1000})  # 1s downstream latency

The included integration test starts nginx behind Toxiproxy, verifies traffic flows through the proxy, then injects a latency toxic and asserts the response is delayed.

PR Checklist

• Your PR title follows the Conventional Commits syntax — uses fix(toxiproxy): as recommended for community modules.
• Your PR allows maintainers to edit your branch.
• The new container is implemented under src/testcontainers/community/toxiproxy/
  • Namespacing follows testcontainers.community.toxiproxy.*.
  • Tests under tests/community/toxiproxy/.
  • docs/community/toxiproxy.rst with the .. autoclass and .. title directives.
  • Feature implemented in __init__.py with corresponding tests. Docs page + example added under docs/modules/ and the nav entry in mkdocs.yml.
• Added in pyproject.toml under project.optional-dependencies as toxiproxy = [] (no extra dependencies).
• Branch is up-to-date.