Move the bottom controls setup (ViewStub inflation, coordinator
creation, native initialization) from synchronous execution during
finishNativeInitialization to a deferred UI task via PostTask. The
synchronous inflation was triggering HardwareRenderer.nNotifyExpensiveFrame
which blocked the main thread waiting for the GPU, causing ANR on
devices under GPU pressure during startup.
This is safe because all consumers of mBottomControlsCoordinatorSupplier
and mTabGroupUiOneshotSupplier already null-check before use, and the
bottom toolbar starts with visibility="gone" making the one-frame delay
imperceptible. The task is wrapped with mCallbackController.makeCancelable()
to auto-cancel during Activity teardown.
Resolves: https://github.com/brave/brave-browser/issues/54077