ZTS: Move largest_pool_001_pos.ksh to Linux runfile

On FreeBSD pools are not allowed to be created using vdevs which are
backed by ZFS volumes. This configuration is not recommended for any
supported platform, nevertheless the largest_pool_001_pos.ksh test
case makes use of it as a convenience. This causes the test case to
fail reliably on FreeBSD. The layout is still tolerated on Linux
so only perform this test on Linux.

Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Ryan Moeller <freqlabs@FreeBSD.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #13166