build: move common headers to common_libcommon_la_SOURCES

build: move common headers to common_libcommon_la_SOURCES

Since we have an libcommon convenience library, I think it would make
sense to put all common headers there, instead of in noinst_HEADERS.

Change-Id: I161e5dc234c46599efbaffcea4e759e2df0ffc96
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/11291
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>