rtc: Disable speed feature high bitdepth mode

Disable the estimate_motion_for_var_based_partition for
cpi->oxcf.use_highbitdepth = 1.

Test case that triggers failures is here, for speed 6:
https://aomedia-review.googlesource.com/c/aom/+/181968
Added speed 6 to that test.

Bug: b/303023614
Change-Id: I4bc1c48637391e66d306219aa7831de6121409cb

av1/encoder/speed_features.c

diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index 218c11b..fd49ada 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -1596,6 +1596,10 @@
     // can be removed once it's fixed for lossless mode.
     sf->hl_sf.accurate_bit_estimate = 0;
   }
+  if (cpi->oxcf.use_highbitdepth) {
+    // Disable for use_highbitdepth = 1 to mitigate issue: b/303023614.
+    sf->rt_sf.estimate_motion_for_var_based_partition = 0;
+  }
 }
 
 // TODO(kyslov): now this is very similar to

test/encode_api_test.cc

diff --git a/test/encode_api_test.cc b/test/encode_api_test.cc
index 94d6d07..f5d3f8b 100644
--- a/test/encode_api_test.cc
+++ b/test/encode_api_test.cc
@@ -343,7 +343,7 @@
     testing::Combine(/*usage=*/testing::Values(AOM_USAGE_GOOD_QUALITY,
                                                AOM_USAGE_REALTIME,
                                                AOM_USAGE_ALL_INTRA),
-                     /*speed=*/testing::Values(7, 10),
+                     /*speed=*/testing::Values(6, 7, 10),
                      /*aq_mode=*/testing::Values(0, 1, 2, 3)));
 
 #if !CONFIG_REALTIME_ONLY