feat!: trace Litestar through its own OpenTelemetryPlugin

[lesnik512]

Why

Litestar ships OpenTelemetryPlugin since 2.22. This replaces LitestarOpenTelemetryInstrumentationMiddleware, our hand-rolled wrapper around OpenTelemetryMiddleware with its WeakKeyDictionary cache of per-next_app instances, so we stop maintaining it. Ported from community-of-python/microbootstrap#154.

What changes

• LitestarOpenTelemetryInstrument appends OpenTelemetryPlugin to application_config.plugins with the installed tracer and meter providers. User plugins are kept.
• The plugin wraps the whole application, so its span starts before routing, when path_template is unknown. A small LitestarOpenTelemetryRouteMiddleware runs inside the route stack and renames the current server span to GET /users/{user_id} and sets http.route. This is the only custom piece left, and it holds no state.
• Exclusions go to the plugin's exclude, which Litestar searches in scope["path"]. Derived paths (metrics, and health when opentelemetry_generate_health_check_spans=False) are anchored as ^/path(?:/|$), so /custom-health/ excludes both slash forms but not /custom-healthy. An empty list is passed as None, because Litestar compiles [] into a pattern that skips every path.
• is_litestar_opentelemetry_installed also requires litestar.plugins.opentelemetry. With Litestar < 2.22 plus OpenTelemetry installed, the instrument is now skipped with a dependency warning instead of failing at import lite_bootstrap.

Breaking

• The litestar-otl extra requires litestar>=2.22 (the litestar extra stays at 2.19).
• opentelemetry_excluded_urls entries are searched in the request path instead of the full URL. Path fragments such as /items/\d+$ behave the same; a pattern anchored on scheme or host (^https?://...) no longer matches.
• Requests to unmatched paths used to produce no server span at all, because the old middleware sat inside the route stack. They now produce a span named after the method alone (GET), without http.route, so scanners cannot inflate span-name cardinality.
• OTEL_PYTHON_LITESTAR_EXCLUDED_URLS is now honored, through the plugin's exclude_urls_env_key.

Tests

• Exported spans carry the route template, unmatched paths get a method-only span, user plugins are kept, the env exclusion works, nothing is excluded when there is nothing to exclude, and the instrument is skipped without litestar.plugins.opentelemetry.
• The tests for the removed middleware's cache and its parsed exclude list are gone.
• just lint and just test pass (343 passed).
• Floor smoke (litestar==2.22.0, opentelemetry-instrumentation-asgi==0.49b0, Python 3.11) passes. At those floors, real requests produce GET /items/{item_id}, GET for a 404 and GET /h for the health route, and /metrics is excluded.