Add sanity.run file

This run file contains a subset of functional tests which exercise
as much functionality as possible while still executing relatively
quickly.  The included tests should take no more than a few seconds
each to run at most.  This provides a convenient way to sanity test a
change before committing to a full test run which takes several hours.

    $ ./scripts/zfs-tests.sh -r sanity
    ...
    Results Summary
    PASS	 813

    Running Time:	00:14:42
    Percent passed:	100.0%

Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes openzfs#11271

tests/runfiles/Makefile.am

@@ -5,4 +5,5 @@ dist_pkgdata_DATA = \
 	linux.run \
 	longevity.run \
 	perf-regression.run \
+	sanity.run \
 	sunos.run

tests/runfiles/common.run

@@ -8,6 +8,12 @@
 # source.  A copy of the CDDL is also available via the Internet at
 # http://www.illumos.org/license/CDDL.
 #
+# This run file contains all of the common functional tests.  When
+# adding a new test consider also adding it to the sanity.run file
+# if the new test runs to completion in only a few seconds.
+#
+# Approximate run time: 4-5 hours
+#
 
 [DEFAULT]
 pre = setup