Start the webview_zygote at boot, but in the background.

This reverts "Delay starting the webview_zygote until first use." but
instead wraps the start in a background task, to avoid blocking the
system server startup waiting for the zygote to be ready.

Bug: 73743583
Bug: 63749735
Bug: 74079433
Test: Verify webview_zygote already running after boot
Change-Id: Iacf968cc2d2857a92c6bacf4012dc88f098c6013
1 file changed