ComponentNegociator::maybeNegotiateByTheme logic does not handle admin theme

Problem/Motivation

In ComponentNegotiator::maybeNegotiateByTheme method, the detection is based on the active theme.

This does not handle the case you have code executed in admin theme context but wanting to negociate definition for a component in the default theme.

For example: An allowed_values_function callback with

  $button = \Drupal::service('plugin.manager.sdc')->negotiateDefinition('ui_suite_bootstrap:button');

Steps to reproduce

Proposed resolution

Instead of themeManager it should be the themeHandler service that should be used.

I will propose a first fix to target default theme, but the logic should be reworked to detect if the replaced component is in admin theme hierarchy or default theme hierarchy.

Remaining tasks

- rework detection logic
- write tests

User interface changes

None

Introduced terminology

None

API changes

Different service injected for Component Negociator.

Data model changes

None

Release notes snippet