Revert^2 "Make IDropBoxManagerService compatible with aidl_interface"

This reverts commit a6efcad3.

Reason for revert: Tweak of original change fixes b/424744354

The following is the delta from the original:

- Move throwing `NullPointerException` on null `tag` fields back to
  `DropBoxManagerService` instead of `DropBoxManager`. This corrects the
  unintended behavior change in the original, where the NPE was moved
  from the binder service itself to the client side manager.
- Rearrange the fields of `IDropBoxManagerService.Entry` to more closely
  match the (former) manual Parcel `DropBoxManager.Entry`.

Bug: 420949170
Bug: 368152571
Test: atest DropBoxManagerTestCpp
Test: atest CtsDropBoxManagerTestCases
Test: atest com.android.devicehealthchecks.SystemAppCheck#system_app_crash
Flag: EXEMPT pure refactor, no API or behavioral changes
Change-Id: Ifc52d1b88fdc2caa602951f98eeb6dd19bf63e47