[a11y] Fix crash when using talkback to add to home screen.

1. Fix a crash from http://cs/android-internal/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java;l=1928;rcl=d677caa75de74f1c3a88367cad67ae405fd2903d. It can also be `ITEM_TYPE_SEARCH_ACTION`. Remove the `itemType` check and just use the `PendingAddItemInfo` class type.
2. Override `startConfigActivity` in `PinShortcutRequestActivityInfo`, so that `Launcher#onActivityResult` can be triggered properly from `Launcher#processShortcutFromDrop` (http://cs/android-internal/packages/apps/Launcher3/src/com/android/launcher3/Launcher.java;l=1939;rcl=d677caa75de74f1c3a88367cad67ae405fd2903d )
3. Then we call to `Launcher#completeAdd` -> `completeAddShortcut`. The original `info` passed to `processShortcutFromDrop` doesn’t have a `componentName` (new code), so remove the component non-null check from `completeAddShortcut`.

Bug: 287166186
Bug: 287167527
Bug: 287166771
Test: manual
Flag: N/A
Change-Id: Id3e1444de188f2d2af760f58e3d9814a2b7abd88