Revert "Move NetworkControllerImpl to @LongRunning thread to prevent @Background from being stuck"

This reverts commit 4db94a0a.

Reason for revert: Performance regression found: b/261773357. I'll rework this with a completely separated thread.

Change-Id: I1ea65fdeeeb1693ba283f446dee9ba92d148442d
Fixes: 261773357