ZTS: Test the correct filesystem_limits behavior

See issue #8226: Property filesystem_limit does not work as documented

There have been previous attempts to fix the behavior on Linux, but so
far the issue is still open.  See PRs #8228, #8280.

The existing tests pass for the incorrect behavior.  This is a problem
on FreeBSD; we are failing the tests because we implement the feature
correctly.

I have adapted the tests based on the work by @loli10k in #8280 and
extended the changes to fix the snapshot_limit test as well.

Linux now fails these tests, so entries linking to the issue have been
added to the "maybe" group in zts-report.py.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10082

tests/test-runner/bin/zts-report.py

@@ -201,6 +201,8 @@ maybe = {
     'history/history_010_pos': ['SKIP', exec_reason],
     'io/mmap': ['SKIP', fio_reason],
     'largest_pool/largest_pool_001_pos': ['FAIL', known_reason],
+    'limits/filesystem_limit': ['FAIL', '8226'],
+    'limits/snapshot_limit': ['FAIL', '8226'],
     'pyzfs/pyzfs_unittest': ['SKIP', python_deps_reason],
     'no_space/enospc_002_pos': ['FAIL', enospc_reason],
     'projectquota/setup': ['SKIP', exec_reason],