[FlowSensitive] [StatusOr] Add test fixture target to Bazel (#180302)

This can be used to make sure downstream extensions to the model still
pass the unit tests.

utils/bazel/llvm-project-overlay/clang/unittests/BUILD.bazel

@@ -115,6 +115,13 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "dataflow_mock_headers",
+    testonly = 1,
+    srcs = ["Analysis/FlowSensitive/MockHeaders.cpp"],
+    hdrs = ["Analysis/FlowSensitive/MockHeaders.h"],
+)
+
 cc_library(
     name = "dataflow_solver_test",
     testonly = 1,
@@ -155,6 +162,28 @@ cc_test(
     ],
 )
 
+cc_library(
+    name = "unchecked_statusor_access_model_test_fixture",
+    testonly = 1,
+    srcs = ["Analysis/FlowSensitive/UncheckedStatusOrAccessModelTestFixture.cpp"],
+    hdrs = ["Analysis/FlowSensitive/UncheckedStatusOrAccessModelTestFixture.h"],
+    deps = [
+        ":dataflow_mock_headers",
+        ":dataflow_testing_support",
+        "//clang:analysis",
+        "//clang:ast",
+        "//clang:ast_matchers",
+        "//clang:basic",
+        "//clang:tooling",
+        "//llvm:Support",
+        "//llvm:TestingADT",
+        "//llvm:TestingAnnotations",
+        "//llvm:TestingSupport",
+        "//third-party/unittest:gmock",
+        "//third-party/unittest:gtest",
+    ],
+)
+
 cc_test(
     name = "analysis_flow_sensitive_tests",
     srcs = glob(