Narrowed typing regression for plugins

Problem/Motivation

Since \Drupal\Core\Plugin\PluginBase added a `create` method, downstream code utilising high level PHPStan is breaking on lack of typing.

Steps to reproduce

I have a plugin that extends \Drupal\Core\Layout\LayoutDefault. My plugin also uses ContainerFactoryPluginInterface.

ContainerFactoryPluginInterface::create has more typing for its $plugin_id parameter.

Now that my pipeline run against core HEAD, the new PluginBase::create takes effect, and shows the PHPStan error:

------ ---------------------------------------------------------------------
35 Parameter #3 $plugin_id (string) of method
MyCustomPlugin::create()
should be contravariant with parameter $plugin_id (mixed) of method
Drupal\Core\Plugin\PluginBase::create()
🪪 method.childParameterType

Proposed resolution

Add the same type information to match the existing ContainerFactoryPluginInterface::create by copying the entire @param section to PluginBase::create. Critically, the `string` for $plugin_id` is added.

Remaining tasks

Implement.

Tests are not required for this change.

This is a documentation only change.

We cannot yet test this/prevent regressions in core because core runs at a low stan version, though there are rumblings on how to get around it (mglaman?)

I want to remind the readers of this issue that core itself does not need to run phpstan level 1000 in order for downstream projects, contrib etc, to run a higher version than core.

User interface changes

None

Introduced terminology

None

API changes

None

Data model changes

None

Release notes snippet

None