Move the Robolectric shadow config up.

In my testing, this reduces the runtime of the Robolectric Settings test
suite on my Z840 workstation from 440 seconds to 402 seconds on average.
By avoiding having a method-level Robolectric shadow import, we avoid
going down a code path which needs to add more shadows later in the
Robolectric execution.

Bug: 64808827
Test: Settings robotests still pass
Change-Id: I7b40d73b30306ae3f9759281afbd7f7266579e24