Merge "Also default shell main thread=true in shell resources" into main

<resources>

    <!-- Determines whether the shell features all run on another thread. This is to be overrided

         by the resources of the app using the Shell library. -->

    <bool name="config_enableShellMainThread">false</bool>

    <bool name="config_enableShellMainThread">true</bool>

    <!-- Determines whether to register the shell task organizer on init.

         TODO(b/238217847): This config is temporary until we refactor the base WMComponent. -->