Make LaunchPerformanceBase and UnitTestSuiteBuilder as APIs

Those two classes are used by many tests using android.test.runner.
Making them as public APIs so that those tests can depend on the public
stub of android.test.runner and stop depending on its implementation
library.

Bug: 157007292
Test: m

Change-Id: I33b458f34ffd4c73430f538a85aac308baa6e010