fix(module:tabs): fix icons position (#2303)

Author: hsuanxyz

components/icon/nz-icon.directive.ts

@@ -123,7 +123,10 @@ export class NzIconDirective extends IconDirective implements OnInit, OnChanges,
       });
       this._classNameObserver.observe(this._elementRef.nativeElement, { attributes: true });
     }
-    this._renderer.addClass(this._elementRef.nativeElement, 'anticon');
+
+    if (!this._el.classList.contains('anticon')) {
+      this._renderer.setAttribute(this._el, 'class', `anticon ${this._el.className}`);
+    }
   }
 
   ngOnDestroy(): void {

components/tabs/nz-tabs-nav.component.html

@@ -4,12 +4,12 @@
 <div class="ant-tabs-nav-container" [class.ant-tabs-nav-container-scrolling]="showPaginationControls" #navContainerElement>
   <span class="ant-tabs-tab-prev" (click)="scrollHeader('before')" [class.ant-tabs-tab-btn-disabled]="disableScrollBefore" [class.ant-tabs-tab-arrow-show]="showPaginationControls">
     <span class="ant-tabs-tab-prev-icon">
-      <i nz-icon type="left" class="ant-tabs-tab-pre-icon-target"></i>
+      <i nz-icon [type]="nzPositionMode === 'horizontal' ? 'left' : 'up'" class="ant-tabs-tab-prev-icon-target"></i>
     </span>
   </span>
   <span class="ant-tabs-tab-next" (click)="scrollHeader('after')" [class.ant-tabs-tab-btn-disabled]="disableScrollAfter" [class.ant-tabs-tab-arrow-show]="showPaginationControls">
     <span class="ant-tabs-tab-next-icon">
-      <i nz-icon type="right" class="ant-tabs-tab-next-icon-target"></i>
+      <i nz-icon [type]="nzPositionMode === 'horizontal' ? 'right' : 'down'" class="ant-tabs-tab-next-icon-target"></i>
     </span>
   </span>
   <div class="ant-tabs-nav-wrap">