[flutter_tools] hot reload/restart update for asset manager change (#66742)

Do not upload all assets on initial devFS sync. This should increase the reliability of the initial connection, even in the face of flaky devfs behavior, in addition to a moderate perf improvement.

Updates fast-start to build assets as part of the initial bundle

Requires flutter/engine#21436
Requires flutter/engine#21586
Requires flutter/engine#21611