feat(router): add "paramsInheritanceStrategy" router configuration option

Previously, the router would merge path and matrix params, as well as
data/resolve, with special rules (only merging down when the route has
an empty path, or is component-less). This change adds an extra option
"paramsInheritanceStrategy" which, when set to 'always', makes child
routes unconditionally inherit params from parent routes.

Closes #20572.

packages/router/src/router_module.ts

@@ -278,6 +278,16 @@ export interface ExtraOptions {
    * current URL. Default is 'ignore'.
    */
   onSameUrlNavigation?: 'reload'|'ignore';
+
+  /**
+   * Defines how the router merges params, data and resolved data from parent to child
+   * routes. Available options are:
+   *
+   * - `'emptyOnly'`, the default, only inherits parent params for path-less or component-less
+   *   routes.
+   * - `'always'`, enables unconditional inheritance of parent params.
+   */
+  paramsInheritanceStrategy?: 'emptyOnly'|'always';
 }
 
 export function setupRouter(
@@ -314,6 +324,10 @@ export function setupRouter(
     router.onSameUrlNavigation = opts.onSameUrlNavigation;
   }
 
+  if (opts.paramsInheritanceStrategy) {
+    router.paramsInheritanceStrategy = opts.paramsInheritanceStrategy;
+  }
+
   return router;
 }