Preload WindowManager Extensions to improve startup performance

WindowManager Extensions is an optional shared library that is required
for WindowManager Jetpack to fully function. Add it to the class loaders
so that it can improve the apps startup performance.

Bug: 269966257
Bug: 266268883
Test: Build and measure the system tracing
Change-Id: I496bb04a06fcd78d4bf246c13528e508c7e0025a