Separate servicestests/utils

The test utility classes under com.android.server.testutils are moved
to servicestests/utils directory in order to easily be shared between
FrameworksServiceTests and upcomming WmTests.

Test: tradefed.sh runAndExitTest FrameworksServicesTests \
    --include-annotation android.platform.test.annotations.Presubmit \
    --exclude-annotation androidx.test.filters.FlakyTest
Bug: 113800711
Change-Id: I39c623a286df1067fffadc25c8a49c12cc05c82c