test(c/driver_manager): Make DriverManifest::SetUp more resilient (#3251)

This fixes an occasional issue with the SetUp block of the
DriverManifest fixture. At least on my macOS system, if a previous test
runs fails before running TearDown, SetUp would fail on this assertion.
This changes the SetUp behavior so it re-uses the temporary directory.

Author: amoeba

c/driver_manager/adbc_driver_manager_test.cc

@@ -414,11 +414,8 @@ class DriverManifest : public ::testing::Test {
          }},
     };
 
-    auto temp_path = std::filesystem::temp_directory_path();
-    temp_path /= "adbc_driver_manager_test";
-
-    ASSERT_TRUE(std::filesystem::create_directories(temp_path));
-    temp_dir = temp_path;
+    temp_dir = std::filesystem::temp_directory_path() / "adbc_driver_manager_test";
+    std::filesystem::create_directories(temp_dir);
 #endif
   }