Component-scoped configuration cascade for the data-grid-accordion. Pass a
withDataGridSkin feature in a parent component's viewProviders array.
Unlike provideDataGridAccordionConfig (root-only),
provideDataGridAccordionConfigAt injects the parent injector's
CNGX_DATA_GRID_ACCORDION_CONFIG value (resolves through the priority chain)
and merges the supplied features on top. Descendant grid instances see the
merged config; sibling sub-trees keep the inherited value untouched.