Fix performance regression

[fzaninotto]

Problem

Inner page components depending on the context render more often than before, and are significantly slower.

Root cause analysis

The introduction of useResourceLabel in #6016 forced a rerender of each view whenever an action is dispatched. That's because this new hook depends on a bad selector that creates a new result each time it is called:

react-admin/packages/ra-core/src/reducer/admin/resource/index.ts

Lines 77 to 78 in f8df1eb

	export const getResources = state =>
	Object.keys(state).map(key => state[key].props);

Therefore, in each of the main page controller (useListController, etc.), any change in the Redux store forces a re-run of the controller, which returns a new object, which updates the page context, which forces a rerender of all the components depending on it.

Solution

Do not use useSelector with that bad selector.

Before

13 renders of the <Datagrid> component in the Post list view in the simple demo:

After

7 renders of the <Datagrid> component in the Post list view in the simple demo: