Canvas AI: Define proper config schema for CanvasAiComponentDescriptionSettingsForm

Overview

The config schema for CanvasAiComponentDescriptionSettingsForm is currently defined as

canvas_ai.component_description.settings:
  type: config_object
  label: 'Canvas AI Component Description Settings'
  mapping:
    component_context:
      type: mapping
      label: 'Component context definitions'
      mapping:
        '*':
          type: component_source_entry
          label: 'Component source entry'

When submiting the form with components from canvas_test_sdc module in a test, the form triggers the following errors

Schema errors for canvas_ai.component_description.settings with the following errors: canvas_ai.component_description.settings:component_context.block missing schema in Drupal\Core\Config\Development\ConfigSchemaChecker->onConfigSave() (line 98 of core/lib/Drupal/Core/Config/Development/ConfigSchemaChecker.php).

This error does not occur when manually saving the form from the UI.
To work around this in the test, I had to add: protected $strictConfigSchema = FALSE; in the test. This issue is created to check this.

Proposed resolution

Investigate the error. Define a better schema.

User interface changes