Create PluginManager class to manage plugin info (#16)

This pull request refactors and simplifies the plugin suggestion and
installation logic for bioio plugins in the `ndevio` package. The main
change is the introduction of the `ReaderPluginManager` class, which
centralizes plugin discovery, installation recommendations, and
messaging. The previous low-level utility functions are now internal,
and the API is streamlined for easier usage and maintenance.

### Plugin Management Refactor

* Introduced the `ReaderPluginManager` class in
`src/ndevio/_plugin_manager.py` and exposed it in the public API via
`src/ndevio/__init__.py`. This class now handles plugin discovery and
installation messaging, replacing direct calls to utility functions.
(`[src/ndevio/__init__.pyR7-R10](diffhunk://#diff-f9e6d85a12005e8899e84eb8c4653f28d9dedf3f40c465cc4271ca98216e485dR7-R10)`)
* Updated the documentation and API of
`src/ndevio/_bioio_plugin_utils.py` to clarify that only low-level
utilities remain, and that users should use `ReaderPluginManager` for
plugin-related tasks.
(`[src/ndevio/_bioio_plugin_utils.pyL1-R23](diffhunk://#diff-db022ea55c4d616954ccf17679356fe2c5c28a861555bb2cdf6fb941c33af079L1-R23)`)

### API Simplification and Cleanup

* Removed several low-level functions from
`src/ndevio/_bioio_plugin_utils.py` (`get_missing_plugins_message`,
`filter_installed_plugins`, `get_installable_plugins`) and replaced them
with a single internal function `format_plugin_installation_message`.
The public API is now limited to `suggest_plugins_for_path` and the
plugin registry.
(`[[1]](diffhunk://#diff-db022ea55c4d616954ccf17679356fe2c5c28a861555bb2cdf6fb941c33af079L127-R195)`,
`[[2]](diffhunk://#diff-db022ea55c4d616954ccf17679356fe2c5c28a861555bb2cdf6fb941c33af079L250-R272)`)
* Simplified the return value of `suggest_plugins_for_path` to just a
list of plugin names, rather than plugin info dicts, making it easier to
use and more consistent.
(`[[1]](diffhunk://#diff-db022ea55c4d616954ccf17679356fe2c5c28a861555bb2cdf6fb941c33af079L224-R213)`,
`[[2]](diffhunk://#diff-db022ea55c4d616954ccf17679356fe2c5c28a861555bb2cdf6fb941c33af079L250-R272)`)

### Integration with Napari Plugin Installer

* Refactored `_open_plugin_installer` in `src/ndevio/_napari_reader.py`
to use the new `ReaderPluginManager` for plugin suggestions and
installation, removing direct calls to utility functions and feasibility
reports.
(`[src/ndevio/_napari_reader.pyL192-R202](diffhunk://#diff-a1495b29f6e07c8278a427f1ad3f4b1033da9353d263c050f0c8d9ac1b2aeebdL192-R202)`)

---

These changes make plugin management more robust, easier to maintain,
and clearer for both internal and external users.

Author: TimMonko

src/ndevio/__init__.py

@@ -4,6 +4,7 @@
     __version__ = "unknown"
 
 from ._napari_reader import napari_get_reader
+from ._plugin_manager import ReaderPluginManager
 from .nimage import nImage
 
-__all__ = ["__version__", "nImage", "napari_get_reader"]
+__all__ = ["__version__", "nImage", "napari_get_reader", "ReaderPluginManager"]