BenchUtiliz: Add missing 'emits' interfaces

These interfaces were missing from the component definition of the
BenchUtiliz component.

BenchUtiliz: support seL4 utilization syscalls

seL4 provides utilization benchmarking syscalls to measure and output
utilization statistics for all threads running in a system. If these
syscalls are configured, as part of idle thread measurements this
component will also start and stop seL4 utilization tracking.

BenchUtiliz: Add IdleThread interface

This interface allows the idle thread measurements to be started and
stopped by another component through a remote procedure call. This can
be used to substitute the serial interface to starting and stopping
measurements for a more sophisticated one provided by a different
component such as a network connection.

BenchUtiliz: Make serial interface optional

Allow this component to be used even if the serial interface isn't
connected.

BenchUtiliz: Move idle thread config internal

The bench_to interface is used as the idle thread which needs to have
the lowest priority and is connected back in on itself to be able to
start the idle thread from the control thread. Make this connection
internal as it is not expected to be changed when integrated into a
project.

global-components: New component to measure utiliz

A camkes component to measure CPU utilization. It contains an interface
that counts the operating time of itself (which should run on the lowest
priority), and a control thread to receive chars from the serial server.