Rename test.

The plan is to test actual Agent behavior in mockingservicestests. This
test only covers the inner TrendCalculator class, so renaming to avoid a
name conflict within the same package.

Bug: 158300259
Test: atest FrameworksServicesTests:AgentTrendCalculatorTest
Change-Id: Id007f2d92293cbdf19fb030b5cd71a3fc23fedb5