Plans Next: Remove `allFeaturesList` prop & `getPlanFeaturesObject` function from plans-grid-next

### What

The `allFeaturesList` prop passed to the grid components and the `getPlanFeaturesObject` function were originally defined to let us create a package while the features-list definitions remained locally in Calypso.

With https://github.com/Automattic/wp-calypso/issues/79004 done, features-list and accessor methods now live in `@automattic/calypso-products`. We can proceed to remove the above concepts and import from the `@automattic/calypso-products` package.

### Why

Clean up temporary and redundant properties and local methods in `plan-grid-next` package.

### How

_No response_

Start in the plans-grid-next package by locating references to the allFeaturesList prop and getPlanFeaturesObject function across the grid components. Trace the existing features-list access through @automattic/calypso-products, remove the redundant local concepts, and verify that the package still builds and its existing checks pass.

Written by the indexing model from the issue text.