[test] Add missing FFI tests to the Fuchsia test package.

Change-Id: I333c5d99051e89b64aca9056b7892d245fda0fe6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/500480
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Ryan Macnak <rmacnak@google.com>

BUILD.gn

@@ -262,6 +262,7 @@ if (is_fuchsia) {
     "tests/ffi/dylib_close_test.dart",
     "tests/ffi/dylib_isolates_test.dart",
     "tests/ffi/dylib_open_test.dart",
+    "tests/ffi/exceptional_return_const_test.dart",
     "tests/ffi/expando_test.dart",
     "tests/ffi/extension_methods_test.dart",
     "tests/ffi/external_typed_data_finalizer_test.dart",
@@ -309,7 +310,9 @@ if (is_fuchsia) {
     "tests/ffi/inline_array_test.dart",
     "tests/ffi/inline_array_variable_length_test.dart",
     "tests/ffi/invoke_callback_after_suspension_test.dart",
+    "tests/ffi/isolate_group_bound_lazy_deopt_test.dart",
     "tests/ffi/isolate_local_function_callbacks_test.dart",
+    "tests/ffi/many_listener_callbacks_test.dart",
     "tests/ffi/msan_test.dart",
     "tests/ffi/native_assets/asset_absolute_test.dart",
     "tests/ffi/native_assets/asset_executable_test.dart",

tools/bots/test_matrix.json

@@ -1694,7 +1694,7 @@
           "name": "vm tests",
           "arguments": [
             "-nvm-${system}-${mode}-${arch}",
-            "-j4",
+            "-j8",
             "ffi"
           ]
         },
@@ -1702,7 +1702,7 @@
           "name": "vm tests",
           "arguments": [
             "-nvm-aot-${system}-${mode}-${arch}",
-            "-j4",
+            "-j8",
             "ffi"
           ]
         }