HarmonyOS promptAction.openCustomDialog 里面的builder内容无法通过expandSafeArea，扩充到安全区域，希望内容视图可以挨着最底边

自定义弹窗仅适用于简单提示场景，不能替代页面使用。由于弹窗存在完全避让输入法行为，即在软键盘弹出时，会自动向上抬起软键盘高度，因此如果弹窗高度过大时，可能会导致部分区域不可见。弹窗避让软键盘时，与软键盘之间存在16vp的安全间距。

弹窗位置调整可以将customStyle设置为true并且给弹窗内部的column布局设置偏移.offset({ x: 0, y: 16})

参考demo如下

// xxx.ets
@CustomDialog
struct CustomDialogExample {
  controller?: CustomDialogController
  cancel: () => void = () => {
  }
  confirm: () => void = () => {
  }
  build() {
    Column() {
      TextInput({ placeholder: "输入内容：" })
        .style(TextInputStyle.Default)
      Row() {
        Text('这是自定义弹窗')
          .height(30)
          .margin(16)
        Image($r("app.media.ic_public_home"))
          .height(30)
          .margin(16)
      }
    }
    .backgroundColor('#F08080')
    .offset({ x: 0, y: 16 })
  }
}

@Entry
@Component
struct CustomDialogUser {
  dialogController: CustomDialogController | null = new CustomDialogController({
    builder: CustomDialogExample({
      cancel: () => {
        this.onCancel()
      },
      confirm: () => {
        this.onAccept()
      }
    }),
    cancel: this.existApp,
    autoCancel: true,
    onWillDismiss: (dismissDialogAction: DismissDialogAction) => {
      console.info("reason=" + JSON.stringify(dismissDialogAction.reason))
      console.log("dialog onWillDismiss")
      if (dismissDialogAction.reason == DismissReason.PRESS_BACK) {
        dismissDialogAction.dismiss()
      }
      if (dismissDialogAction.reason == DismissReason.TOUCH_OUTSIDE) {
        dismissDialogAction.dismiss()
      }
    },
    alignment: DialogAlignment.Bottom,
    offset: { dx: 0, dy: 0 },
    customStyle: true,
    width: "100%",
    // gridCount:4,
    cornerRadius: 0,
    backgroundColor: Color.White,
  })

  // 在自定义组件即将析构销毁时将dialogController置空
  aboutToDisappear() {
    this.dialogController = null // 将dialogController置空
  }

  onCancel() {
    console.info('Callback when the first button is clicked')
  }

  onAccept() {
    console.info('Callback when the second button is clicked')
  }

  existApp() {
    console.info('Click the callback in the blank area')
  }

  build() {
    Column() {
      Button('click me')
        .onClick(() => {
          if (this.dialogController != null) {
            this.dialogController.open()
          }
        })
        .backgroundColor(0x317aff)
        .margin(50)
    }.width('100%').margin({ top: 5 })
  }
}