[Bedstead] Fix build warnings in dpmwrapper

This CL is a combination of the CL chain starting at http://ag/35289551
- and then some more, as requested by the reviewer.

It does the following things:

- Modify ServiceManagerWrapper's interface to deal with non-nullable
  types only. This was already true; the contract was not explicit
  though in Java. Now that we are using Kotlin, we can enforce that.
- Fix DevicePolicyManagerWrapper to use Kotlin style stubs instead of
  Java ones. Additionally, fix an error from http://ag/35256892 where
  Java `any()` got converted to Kotlin `any()`. Java's `any()` actually
  corresponds to Kotlin's `anyOrNull()`.
- Divide up spy setup in DevicePolicyManagerWrapper into individual
  methods. This solves the underlying problem in b/441373957
- Fix GenericManagerWrapper, HardwarePropertiesManagerWrapper,
  TetheringManagerWrapper, UserManagerWrapper, WifiManagerWrapper to
  use Kotlin style stubs instead of Java ones.
- Fix build warnings related to calling deprecated Java APIs while
  setting up stubs.

Bug: 441036343
Bug: 441036939
Test: m DpmWrapper
Flag: TEST_ONLY
Change-Id: I88cf7413c29ae687ee2e2943085ca51d54e24b7a
7 files changed