Enable partitioned index/filter in stress tests (#5895)

Summary:
This is the 2nd attempt after the revert of https://github.com/facebook/rocksdb/pull/4020
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5895

Test Plan:
```
./tools/db_crashtest.py blackbox --simple --interval=10 --max_key=10000000
```

Differential Revision: D17822137

Pulled By: maysamyabandeh

fbshipit-source-id: 3d148c0d8cc129080410ff859c04b544223c8ea3

tools/db_crashtest.py

@@ -41,8 +41,8 @@ default_params = {
     "enable_pipelined_write": 0,
     "expected_values_path": expected_values_file.name,
     "flush_one_in": 1000000,
-    # Temporarily disable hash and partitioned index
+    # Temporarily disable hash index
-    "index_type": 0,
+    "index_type": lambda: random.choice([0,2]),
     "max_background_compactions": 20,
     "max_bytes_for_level_base": 10485760,
     "max_key": 100000000,
@@ -51,7 +51,7 @@ default_params = {
     "nooverwritepercent": 1,
     "open_files": lambda : random.choice([-1, 500000]),
     # Temporarily disable partitioned filter
-    "partition_filters": 0,
+    "partition_filters": lambda: random.randint(0, 1),
     "prefixpercent": 5,
     "progress_reports": 0,
     "readpercent": 45,
@@ -179,8 +179,10 @@ def finalize_and_sanitize(src_params):
         # now assertion failures are triggered.
         dest_params["compaction_ttl"] = 0
     if dest_params["partition_filters"] == 1:
-        dest_params["index_type"] = 2
+        if dest_params["index_type"] != 2:
-        dest_params["use_block_based_filter"] = 0
+            dest_params["partition_filters"] = 0
+        else:
+            dest_params["use_block_based_filter"] = 0
     return dest_params
 
 

tools/db_stress.cc

@@ -354,8 +354,7 @@ DEFINE_bool(use_block_based_filter, false, "use block based filter"
               "instead of full filter for block based table");
 
 DEFINE_bool(partition_filters, false,
-            "use partitioned filters "
+            "use partitioned filters for block-based table");
-            "for block-based table");
 
 DEFINE_int32(
     index_type,