cpu: Move host_tid field to CPUState

Change cpu_index() argument to CPUState now that it is no longer used.

Signed-off-by: Andreas Färber <afaerber@suse.de>
cpu: Move running field to CPUState

Pass CPUState to cpu_exec_{start,end}() functions.

Signed-off-by: Andreas Färber <afaerber@suse.de>
cpu: Move exit_request field to CPUState

Since it was located before breakpoints field, it needs to be reset.

Signed-off-by: Andreas Färber <afaerber@suse.de>