CI: add new zfs-tests workflow

[gmelikov]

Requires #11296 to finish successfully.

Motivation and Context

• Use free github resources to run our tests
• Run only main tests to get sanity check of PR fast, later we can use it as a prerequisite for other jobs

Description

Run zfs-tests with sanity.run for brief results. Last run was 27m 39s long.

How Has This Been Tested?

https://github.com/gmelikov/zfs/runs/1512086945?check_suite_focus=true

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)
• CI enhancement

[gmelikov]

Hm, I've got one test killed lately, but it's not frequent, I see it first time

Test: /usr/share/zfs/zfs-tests/tests/functional/log_spacemap/log_spacemap_import_logs (run as root) [01:07] [KILLED]
18:43:56.79 SUCCESS: zpool create -o cachefile=none -f logsm_import loop0
18:43:56.82 SUCCESS: zfs create logsm_import/fs
18:43:56.83 SUCCESS: dd if=/dev/urandom of=/logsm_import/fs/00 bs=128k count=10
18:43:56.89 SUCCESS: sync
18:43:56.90 SUCCESS: dd if=/dev/urandom of=/logsm_import/fs/00 bs=128k count=10
18:43:56.91 SUCCESS: sync
18:43:56.92 SUCCESS: set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 1
18:43:56.96 SUCCESS: zpool export logsm_import
18:44:31.24 SUCCESS: set_tunable64 METASLAB_DEBUG_LOAD 1
18:45:04.54 SUCCESS: zpool import logsm_import
18:45:04.54 Log spacemaps imported with no errors
18:45:04.54 NOTE: Performing local cleanup via log_onexit (cleanup)
18:45:04.55 SUCCESS: set_tunable64 KEEP_LOG_SPACEMAPS_AT_EXPORT 0
18:45:04.55 SUCCESS: set_tunable64 METASLAB_DEBUG_LOAD 0
18:45:04.61 SUCCESS: zpool destroy -f logsm_import