cmd/plugin/show: use entrypoint distro name

Prior to this change the `plugin show` command assumed the entrypoint
name to be the same as the package providing the plugin. This change
makes use of the `entrypoint.distro.name` instead to derive the source
package.

Resolves: python-poetry#5417

src/poetry/console/commands/plugin/show.py

@@ -52,7 +52,7 @@ def handle(self) -> int:
             if issubclass(plugin, ApplicationPlugin):
                 category = "application_plugins"
 
-            package = packages_by_name[canonicalize_name(entry_point.name)]
+            package = packages_by_name[canonicalize_name(entry_point.distro.name)]
             plugins[package.pretty_name]["package"] = package
             plugins[package.pretty_name][category].append(entry_point)