Unmute Osiris tests and temporarily disable multithreading (#10737)

Author: alexvru

.github/config/muted_ya.txt

@@ -209,7 +209,4 @@ ydb/core/tx/schemeshard/ut_pq_reboots TPqGroupTestReboots.CreateMultiplePqTablet
 ydb/tests/functional/serializable test.py.test_local
 ydb/core/blobstorage/ut_vdisk TBsVDiskGC.GCPutKeepBarrierSync
 ydb/core/blobstorage/ut_vdisk TBsVDiskManyPutGet.ManyPutRangeGetCompactionIndexOnly
-ydb/core/blobstorage/ut_blobstorage/ut_osiris Osiris.block42
-ydb/core/blobstorage/ut_blobstorage/ut_osiris Osiris.mirror3dc
-ydb/core/blobstorage/ut_blobstorage/ut_osiris Osiris.mirror3of4
 ydb/core/blobstorage/ut_mirror3of4 Mirror3of4.ReplicationSmall

ydb/core/blobstorage/ut_blobstorage/osiris.cpp

@@ -4,7 +4,7 @@
 #include <util/system/condvar.h>
 #include <util/system/info.h>
 
-#define SINGLE_THREAD 0
+#define SINGLE_THREAD 1
 
 namespace {