Add the trace chunk and trace chunk registry interfaces

Add the trace chunk and trace chunk registry interfaces

A trace chunk is a set of stream files. It maps to the user-visible
concept of "trace archive chunks" produced following a tracing session
rotation.

The concept of a "chunk" is introduced to make it possible to
associate a group of stream files together, store common
properties (e.g. the epoch, base path, list of files, credentials,
etc.), and perform an action once all files have been closed/released.

The "trace chunk" interface is to be used by the session, consumer,
and relay daemons in different ways, through the OWNER or USER roles.

The lttng_dynamic_pointer_array, lttng_dynamic_array, and optional
utils are added since they are used by the trace chunk implementation.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>