fix(material/sidenav): allow focus to escape to sidenav container

When the new `ConfigurableFocusTrap` is passed to a sidenav, it prevents focus from
moving from the sidenav to the container.

These changes pass in a predicate that allows for focus to escape.

Fixes #21955.

Author: crisbeto

src/material/sidenav/drawer.ts

@@ -354,7 +354,10 @@ export class MatDrawer implements AfterContentInit, AfterContentChecked, OnDestr
   }
 
   ngAfterContentInit() {
-    this._focusTrap = this._focusTrapFactory.create(this._elementRef.nativeElement);
+    this._focusTrap = this._focusTrapFactory.create(this._elementRef.nativeElement, {
+      defer: false,
+      focusEscapePredicate: target => !!this._container?._element.nativeElement.contains(target)
+    });
     this._updateFocusTrapState();
   }
 
@@ -593,7 +596,7 @@ export class MatDrawerContainer implements AfterContentInit, DoCheck, OnDestroy
   }
 
   constructor(@Optional() private _dir: Directionality,
-              private _element: ElementRef<HTMLElement>,
+              public _element: ElementRef<HTMLElement>,
               private _ngZone: NgZone,
               private _changeDetectorRef: ChangeDetectorRef,
               viewportRuler: ViewportRuler,

tools/public_api_guard/material/sidenav.d.ts

@@ -59,6 +59,7 @@ export declare class MatDrawerContainer implements AfterContentInit, DoCheck, On
         right: number | null;
     };
     _drawers: QueryList<MatDrawer>;
+    _element: ElementRef<HTMLElement>;
     _userContent: MatDrawerContent;
     get autosize(): boolean;
     set autosize(value: boolean);