common: index and trace-chunk file creation/open API change

common: index and trace-chunk file creation/open API change

An API change to the common libraries is required for the following
functions to accomodate the clear feature:

- lttng_trace_chunk_open_file(),
- lttng_index_file_create_from_trace_chunk(),
- lttng_index_file_create_from_trace_chunk_read_only().

An "expect_no_file" boolean is introduced, allowing specific invocation
to consider a ENOENT errno as an expected condition (and not an error).
This is the case for instance for relayd live viewer_stream_rotate(),
which can fail to open files in the new chunk after a clear with per-pid
buffers. Same goes for viewer_get_next_index() and try_open_index().

Change the lttng_index_file_create_from_trace_chunk_read_only and
lttng_index_file_create_from_trace_chunk to allow them to return
a chunk status, which allows the callers to distinguish between
errors and a "no file" status, and deal with the situation accordingly.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I3c43edca01629488c4e777078db7ffd2e88dc7ea
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>