xattr dataset prop: change defaults to sa

It's the main recommendation to set xattr=sa
even in man pages, so let's set it by default.

xattr=sa don't use feature flag, so in the worst
case we'll have non-readable xattrs by other
non-openzfs platforms.

Non-overridden default `xattr` prop of existing pools
will automatically use `sa` after this commit too.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: George Melikov <mail@gmelikov.ru>
Closes #15147

tests/zfs-tests/tests/functional/projectquota/projectid_003_pos.ksh

@@ -59,7 +59,7 @@ log_onexit cleanup
 
 log_assert "Check changing project ID with directory-based extended attributes"
 
-log_must zfs set xattr=on $QFS
+log_must zfs set xattr=dir $QFS
 
 log_must touch $PRJGUARD
 log_must chattr -p $PRJID1 $PRJGUARD
@@ -76,6 +76,6 @@ sync_pool
 typeset prj_aft=$(project_obj_count $QFS $PRJID1)
 
 [[ $prj_aft -ge $((prj_bef + 5)) ]] ||
-	log_fail "new value ($prj_aft) is NOT 5 largr than old one ($prj_bef)"
+	log_fail "new value ($prj_aft) is NOT 5 larger than old one ($prj_bef)"
 
 log_pass "Changing project ID with directory-based extended attributes pass"

tests/zfs-tests/tests/functional/xattr/xattr_001_pos.ksh

@@ -52,7 +52,7 @@ function cleanup {
 	fi
 }
 
-set -A args "on" "sa"
+set -A args "dir" "sa"
 
 log_assert "Create/read/write/append of xattrs works"
 log_onexit cleanup

tests/zfs-tests/tests/functional/xattr/xattr_002_neg.ksh

@@ -46,7 +46,7 @@ function cleanup {
 
 }
 
-set -A args "on" "sa"
+set -A args "dir" "sa"
 
 log_assert "A read of a non-existent xattr fails"
 log_onexit cleanup