Cache plugin instances for better performance

Problem/Motivation

When rendering complex sites, with a lot of components, especially with components that inherit each other over multiple levels, the rendering itself gets very slow. It seems it gets exponentially slower with each level of inheritance / embedding.

Steps to reproduce

Build 3 components that build on top of each other and render a lot of them. When we compare the render time of using the direct name of the component in the embed / include (so cl_components resolves the component and does its magic) it is painfully slow in comparison to loading the direct path of the twig file or the component via the components module (with "@modulename/path/to/twigfile").

Proposed resolution

Cache Plugin instances, because it seems that they get created on the fly for each call to a component and that creates a big performance hit.

Remaining tasks

Create issue fork / proposed resolution (Harlor has a POC we created together when we were debugging the performance of our project)

User interface changes

None