CPU topology statedump on x86

CPU topology statedump on x86

New statedump tracepoint to dump the active CPU/NUMA topology. This
allows to know which CPUs are SMT sibling or on the same socket. For now
only x86 is supported because all architectures has different fields.
The field "architecture" is statically defined and should be present in
all implementations so parsing tools know what content to expect.

Example output:
lttng_statedump_cpu_topology: { cpu_id = 3 }, { architecture = "x86",
	cpu_id = 0, vendor = "GenuineIntel", family = 6, model = 142,
	model_name = "Intel(R) Core(TM) i7-7600U CPU @ 2.80GHz",
	physical_id = 0, core_id = 0, cores = 2 }

Signed-off-by: Julien Desfossez <jdesfossez@digitalocean.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>