fstests: scale some tests for high CPU count sanity

fstests: scale some tests for high CPU count sanity

Several tests use lots of processes to stress the filesystem. many
of them haven't really considered what this means for running the
test on high CPU machines (e.g. >32p) and the potential contention
and performance issues this might trigger.

Some of these tests simply need to increase the size of the journal.
Some need to run on filesystems with high inherent concurrency (e.g.
larger AG count). Some need more efficient/faster file creation. And
so on.

This commit is a collection of those sorts of changes to improve
runtimes on high CPU count machines.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Zorro lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>