Call 'cacheBackend' directly instead of using UseCacheBackendTrait

Problem/Motivation

Due to oEmbed services require a cache backend, ProviderRepositoryDecorator needs updated.

Proposed resolution

• Disuse UseCacheBackendTrait
• Call 'cacheBackend' directly instead
• Update constructor to make $cache_backend parameter required

There shouldn't be any backwards compatible issues. ProviderRepositoryDecorator is a final class.

Remaining tasks

Write a patch

User interface changes

None

API changes

$cache_backend parameter now required for the ProviderRepositoryDecorator constructor.

Data model changes

None.