Build, Test: Scheduler: Split up cts/scheduler directory
After a few more scheduler tests are introduced, make distdir-am will
begin to fail with "Argument list too long" due to the size of
$dist_files. It seems the simplest way to avoid this is to split up the
cts/scheduler directory into multiple subdirectories, each with its own
Makefile.
IMO it makes the most sense to split it based on file extension. That
way, each subdir (besides stderr) has an equal number of files, and they
should all grow at the same rate so that they don't have to be
rebalanced later (as could be required for a grouped alphabetical
split). This approach also requires few changes to cts-scheduler.in.
This should cut $dist_files for each sub-make into 20% of its former
size, allowing plenty of room for growth.
Signed-off-by: Reid Wahl <nrwahl@protonmail.com>