ProviderInfo: record provider module path to remove the package-name → module heuristic in example DAG bundle discovery

### Description

`_add_provider_example_dags_to_bundle` in [`airflow-core/src/airflow/dag_processing/bundles/manager.py`](https://github.com/apache/airflow/blob/main/airflow-core/src/airflow/dag_processing/bundles/manager.py) currently derives the Python package path of an installed provider from its distribution name with a string heuristic:

```python
if package_name.startswith("apache-airflow-providers-"):
suffix = package_name[len("apache-airflow-providers-") :]
module_name = "airflow.providers." + suffix.replace("-", ".")
else:
module_name = package_name.replace("-", "_")
```

This works for canonical Apache providers because they follow a fixed layout convention, but it has known weak points:

- third-party providers whose distribution name does not start with `apache-airflow-providers-` fall back to a naive `replace("-", "_")` which is often wrong;
- the dash-to-dot reverse is lossy: `foo-bar` and `foo_bar` both come back as `foo.bar`.

### Why `entry_point.module` does not directly solve this

Provider entry points are declared as e.g. `airflow.providers.standard.get_provider_info:get_provider_info`. `entry_point.module` resolves to the `get_provider_info` *module file*, not the package, so `importlib.import_module(entry_point.module)` returns a module without `__path__`. Walking `__path__` to find `example_dags/` would iterate zero times.

### Proposed approach

Extend `ProviderInfo` in [`shared/providers_discovery/src/airflow_shared/providers_discovery/providers_discovery.py`](https://github.com/apache/airflow/blob/main/shared/providers_discovery/src/airflow_shared/providers_discovery/providers_discovery.py) to record the parent package path of each discovered provider:

- derive it from `entry_point.module` by stripping the trailing `.get_provider_info` segment, or
- surface it from the dist metadata (`dist.files`, `top_level.txt`, etc.).

Mirror the field on `airflow.providers_manager.ProviderInfo` so consumers in `airflow-core` can read it.

### Acceptance criteria

- `ProviderInfo` exposes a stable attribute (e.g. `module_path` or `package_module`) populated for every discovered provider.
- The heuristic block in `_add_provider_example_dags_to_bundle` is replaced with a direct `importlib.import_module(info.module_path)` lookup.
- The tracking comment `# tracked at ` in `manager.py` is removed.
- Tests cover both canonical Apache providers (`apache-airflow-providers-standard`, `apache-airflow-providers-common-sql`) and a synthetic third-party provider with a non-canonical distribution name.

### Context

Surfaced during review of #66161 (https://github.com/apache/airflow/pull/66161) by @potiuk and @jscheffl. Deferred to keep that PR focused on the example-DAG-bundle migration; this issue captures the proper fix.