SDC: Add a method to retrieve only components not replaced by others

Problem/Motivation

We are planning to rewrite UI Patterns upon SDC. To achieve this, we are proposing a few changes and additions:

• #3390980: Make SDC extensible
• #3352063: Allow schema references in Single Directory Component prop schemas
• #3390712: Add component variants to SDC
• #3390717: Allow declaration of template path in SDC
• #3391702: SDC ComponentElement: Transform slots scalar values to #plain_text instead of throwing an exception
• Add a method to retrieve only components not replaced by others. The current issue

ComponentPluginManager::getAllComponents() is useful to retrieve all the components.

However, we sometimes needs a list of the components minus the ones replaced by others. For example:

• An UI for selecting components while doing site building
• A library page
• Some controls in code

A replaced component is not "active" anymore, so it makes little sense to display it.

Proposed resolution

Add a boolean parameter to ComponentPluginManager::getAllComponents():

public function getAllComponents(bool $filter = FALSE): array {

For better control, this parameter can be an integer like what is done in StreamWrapperManagerInterface::getWrappers:

public function getAllComponents(int $filter = 0): array {

Or add a new public function to ComponentPluginManager:

public function getActiveComponents(): array {

I guess "active" a good keyword for components which are not replaced by others. So, we can add other unrelated rules later (according to some status or conditions).

Remaining tasks

If there is a chance for this feature to be accepted, we (UI Patterns team) can propose a merge request soon.

We have one month before the release of Drupal 10.2.0-alpha1.