Avoid using IconCompat.createFromIcon() that doesn't support bitmap icons

[canyie]

This is a regression introduced in e9b76b6:

From the source code of IconCompat.createFromIcon(), bitmap icons will be treated as TYPE_UNKNOWN:
https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:core/core/src/main/java/androidx/core/graphics/drawable/IconCompat.java;l=1110

And IconCompat.addToShortcutIntent() does not support TYPE_UNKNOWN:
https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:core/core/src/main/java/androidx/core/graphics/drawable/IconCompat.java;l=698

So it will crash on Android before 8.0:

 java.lang.IllegalArgumentException: Icon type not supported for intent shortcuts
    at androidx.core.graphics.drawable.IconCompat.addToShortcutIntent(IconCompat.java:754)
    at androidx.core.content.pm.ShortcutInfoCompat.addToIntent(ShortcutInfoCompat.java:213)
    at androidx.core.content.pm.ShortcutManagerCompat.requestPinShortcut(ShortcutManagerCompat.java:204)
    at com.topjohnwu.magisk.view.Shortcuts.addHomeIcon(Shortcuts.kt:36)
    at com.topjohnwu.magisk.ui.MainActivity$askForHomeShortcut$1$2$1.invoke(MainActivity.kt:227)
    at com.topjohnwu.magisk.ui.MainActivity$askForHomeShortcut$1$2$1.invoke(MainActivity.kt:226)
    at com.topjohnwu.magisk.view.MagiskDialog$ButtonViewModel.clicked(MagiskDialog.kt:122)
    at com.topjohnwu.magisk.databinding.DialogMagiskBaseBindingImpl._internalCallbackOnClick(DialogMagiskBaseBindingImpl.java:562)
    at com.topjohnwu.magisk.generated.callback.OnClickListener.onClick(OnClickListener.java:11)
    at android.view.View.performClick(View.java:5205)